UC-NRLF 
 
-FROM'THE* 
 SCIENTIFIC- LIBRARY-OF- 
 
 JACQUES -LOEB- 
 
THE CKOONIAN LECTURES 
 
 ON THE 
 
 CHEMICAL SIDE OF NEKYOUS ACTIVITY 
 
THE CROONIAN LECTURES 
 
 ON THE 
 
 CHEMICAL SIDE OF NERVOUS 
 ACTIVITY 
 
 Delivered before the Royal College of Physicians of London, in 
 
 June, 1901 
 
 BY 
 
 W. D. HALLIBUETON, M.D., F.E.S. 
 i( 
 
 Fellow of the College of Physicians ; Professor of Physiology, King's College, 
 
 London 
 
 lonton 
 
 JOHN BALE, SONS & DANIELSSON, LTD. 
 
 OXFORD HOUSE 
 
 83-89, GREAT TITCHFIELD STREET, W. 
 1901 
 
A/3 
 
 G 
 
 BIOLOGY 
 LIBRARY 
 
 Q 
 
PREFACE. 
 
 THE lectures as now printed are somewhat fuller than those 
 actually delivered. Analytical tables are for instance given, and 
 details of experiments are described, which were only referred to 
 in general terms in the spoken lectures. This little book aims at 
 presenting in a systematic way the numerous researches relat- 
 ing to the nervous system which for several years past have been 
 carried out in the Physiological Laboratory of King's College, 
 London. Much of what appears has been published elsewhere, 
 mainly in the Journal of Physiology, and in the Philosophical 
 Transactions of the Eoyal Society, but I have never before had 
 the opportunity of presenting the whole in a connected form. 
 The fourth lecture is in the main identical with a paper recently 
 presented by Dr. Mott and myself to the Royal Society. 
 
 I have to thank the Council of the Royal Society, the Editors 
 of the Journal of Physiology, and of the British Medical Journal, 
 Dr. Mott, and Mr. John Murray, for permission to reproduce 
 some of the illustrations here given. 
 
 I have also to thank the Royal College of Physicians for 
 allowing the funds of the Croonian Trust to be devoted to the 
 expenses of many of the researches here described. 
 
 Kings College. W. D. HALLIBURTON. 
 
 December, 1901. 
 
 778G49 
 
CONTENTS. 
 
 LECTURE 1. THE CHEMICAL COMPOSITION OF NERVOUS TISSUES. 
 
 Introductory. Relation of water and solids. Specific gravity. 
 Solids of nervous tissues. Proteids. Protagon and lecithin. 
 The cerebrospinal fluid 1 
 
 LECTURE 2. METABOLISM IN NERVOUS TISSUES. 
 
 Anabolism and katabolisrn. Necessity for oxygen. Reaction. 
 Production of carbonic acid. Evidence of metabolic activity 
 derived from the examination of cerebrospinal fluid, and 
 saline extracts of nervous tissues. Fatigue. Micro-chemical 
 methods ; Golgi's method ; Nissl's method. Sleep and 
 narcosis 21 
 
 LECTURE 3. PATHOLOGICAL SIDE OF THE SUBJECT. 
 
 The coagulation temperature of cell-globulin and its bearing on 
 hyperpyrexia. Chemical pathology of General Paralysis of 
 the Insane. Physiological action of choline and neurine ... 42 
 
 LECTURE 4. THE CHEMISTRY OF NERVE DEGENERATION. 
 
 Examination of the blood in cases of nervous disease in man. 
 Experiments on animals ; observations on the blood ; chemi- 
 cal examination of degenerated nerves ; histological exami- 
 nation of degenerated nerves. Correlation of chemical and 
 histological characters. The chemical meaning of the 
 March! reaction. General conclusions 63 
 
THE CROONIAN LECTTJBES 
 
 ON 
 
 THE CHEMICAL SIDE OF NERVOUS 
 ACTIVITY. 
 
 LECTUKE I. 
 THE CHEMICAL COMPOSITION OF NEEVOUS TISSUES. 
 
 MR. PRESIDENT AND FELLOWS, My first duty is to thank you 
 for the honour you have conferred upon me in electing me 
 Croonian Lecturer for the present year. I feel the responsibility 
 a heavy one, and I can only trust that the subject I have chosen 
 may be shown to possess important bearings not only to physi- 
 ologists, but also to those who, like the majority of my hearers, 
 devote their studies to the healing of the sick. 
 
 On looking through the list of previous Croonian lecturers, 
 one is at once struck with the large number who have selected 
 the nervous system as their subject. The reason for this is not 
 far to seek. The subject is a complex one ; hence its fascination 
 both for physiologists and physicians. It is the ruling system of 
 the body which regulates and controls the other processes which 
 occur there. It is, moreover, the seat of mental phenomena, and 
 it therefore touches deep questions of being and consciousness ; 
 its investigation appeals to all those who have sought to unravel 
 the so-called mysteries of thought and reason. To discover the 
 secrets of the mind has ever been the bent of philosophic 
 thinkers, and to ascertain the way in which the mind works, 
 investigators have directed their attention to the organ of mind, 
 the brain. Some have traced the devious channels of this organ 
 with the scalpel, others with the microscope ; others again, have 
 1 
 
2 *f .* . V 3:k^ -OltOONIAN LECTURES ON THE 
 
 method to establish the localisation of 
 cerebral functions. All these investigations have gone hand in 
 hand with the researches of pathologists and clinical observers, 
 who in the sick room and at the autopsy have obtained little by 
 little knowledge of the nervous lesions which lie at the root of 
 mental and nervous diseases. 
 
 The mass of knowledge which has now accumulated as the 
 result of all this work is very immense, and these lectures have 
 frequently been the channel by which the fruits of such labour 
 have been laid before the medical profession. The enormous 
 benefit which has thereby accrued to suffering humanity it is 
 hardly necessary to emphasise before my present audience. The 
 feats of cerebral localisation alone, which have rendered brain 
 surgery a matter of every-day experience, are in themselves suffi- 
 cient as an illustration of this fact. 
 
 In spite, however, of this increase of scientific and accurate 
 knowledge, and in spite of its paramount usefulness, we must 
 still confess that any real information of the deeper meaning of 
 volition and consciousness is lacking. We may theorise and 
 argue as before, but any visible or tangible means of testing our 
 theories in the light of experiment seems as far off as ever. 
 
 No scalpel however skilful, no microscope however powerful, 
 no stain however delicate, has yet succeeded in unearthing that 
 intangible something we call the mind. The methods of that 
 new branch of physiology which is termed experimental 
 psychology are also at present equally inefficacious to solve the 
 problem. 
 
 We sometimes speak of physiology as the application of the 
 laws of chemistry and physics to life. Since this conception of 
 the aim and object of physiology has pervaded its disciples, the 
 progress of physiological knowledge has been rapid and fruitful. 
 When Helmholtz, Ludwig, and their contemporaries set them- 
 selves to rescue our science from the slough of mysticism, they 
 placed it on a firm basis, and no doubt hoped in time to be able 
 to expunge the word " vital " from their vocabulary. But all 
 must admit that that time has not yet arrived. The neo-vitalists, 
 it is true, have not the same contented and reverent frame of 
 mind in relation to the meaning of the word vital as the older 
 vitalists had. They admit its unsatisfactory and unscientific 
 nature ; they use it merely as a convenient expression for what 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 3 
 
 cannot at present be brought into line with the forces that 
 operate in the inorganic world, and not merely as a cloak for 
 their ignorance. The use of this word becomes most frequent 
 when we have to deal with mental phenomena, and the question 
 for the future is whether the manifestations of vitality are only 
 physical and chemical after all, or whether there is really some 
 other, and at present unknown force, or unknown aspect of 
 known forces, which in the meanwhile we must be content to 
 label as vital. 
 
 On such a fundamental question as this, there is obviously 
 much room for differences of opinion. The answer is certainly 
 in the region of the unknown ; some may place it with du Bois 
 Reymond in the region of the unknowable. That may be so ; 
 one hopes that it is not, for if we once admit that any subject is 
 unknowable we place an impenetrable bar upon research, and 
 remove any stimulus to investigate it afresh. 
 
 My object in these lectures is a much more commonplace one 
 than the investigation of such fundamental problems. I propose 
 to lay before you the principal known facts concerning the 
 chemical structure of nervous tissues, and the changes of a 
 chemical nature that occur in activity, death, and disease of 
 these tissues. This is a side of the subject which has been com- 
 paratively neglected. A great deal of work has been done, it is- 
 true, but the amount is small in comparison with that which 
 has been carried out from the anatomical and microscopic stand- 
 point. The scalpel and the microscope have not succeeded in 
 discovering the mind ; we should not therefore expect to find it 
 in a test-tube. Still, even in our test-tubes we shall find some- 
 thing that is of interest, and I hope also of practical importance. 
 The chemical investigator has a great disadvantage when he 
 sets himself to study the composition of living matter, for his 
 reagents, however gentle they may be, kill the object of his 
 research, and he can then examine not living protoplasm, but 
 only its ruins. In spite of this, chemical physiology is advancing 
 with rapid strides, and I am convinced that chemical pathology 
 has a great future before it ; and the more study I devote to the 
 consideration of pathological problems, the more deeply do I feel 
 that chemistry is a most powerful ally in solving them. 
 
 If in what I have now to say I dwell more particularly on 
 my own researches and on those carried out by others in my 
 
4 THE CROONIAN LECTURES ON THE 
 
 laboratory, I do so not because I consider them more worthy of 
 attention or of greater importance than the work which has been 
 pursued elsewhere, but because I shall be limited by time, and 
 further, because I understand that one object of this lectureship 
 is to give an investigator the opportunity of presenting his own 
 original work in a connected and orderly way before the medical 
 public. I would here at the outset express my thanks to those 
 who have worked with me, and more particularly to Dr. Mott 
 and Dr. Brodie. 
 
 For the last five years Mott and I have laboured together, 
 and much of what I have to say is his work rather than my own. 
 In being associated with him I have had the great advantage of 
 working not only with a pathologist, but also with a practical 
 physician, and this will enable me to insist more forcibly than 
 I should otherwise have been able to do on the practical applica- 
 tion of our investigations to the every-day life of the practising 
 medical man. 
 
 In his Croonian lectures last year, Dr. Mott laid before you 
 some of our joint work ; my lectures will supplement and extend 
 some of the points he dwelt upon then, in the light of the work 
 we have carried out during the last twelve months. In order to 
 render the subject more complete, it will of course be necessary 
 ior me to mention the work of many others, and I think that in 
 -the end our conclusion will be not one of satisfaction at the 
 accomplishment of so much, but rather a realisation of the vast 
 field still hardly touched, and an earnest hope that more labourers 
 will enter and assist in the endeavour to reduce t he gaps in our 
 knowledge. 
 
 Before it is possible to pass on to a study of pathological 
 questions, I must ask your indulgence if for a time I dwell upon 
 some details in connection with the physiological side of the 
 subject, and the first of these which I will take up is the general 
 chemical composition of the various parts which make up the 
 nervous system. 
 
 EELATION OF WATEK AND SOLIDS. 
 
 The first general impression one derives from a glance through 
 any of the analytical tables in the text-books, is the great pre- 
 ponderance of water in most of our so-called solid tissues. Even 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY O 
 
 bone contains nearly 50 per cent, of water, and when Hamlet 
 expresses the wish that this too solid flesh would melt, he spoke 
 without the knowledge that his muscles contained only 25 per 
 cent, of solid material. The nervous system is no exception to 
 this rule. The amount of water varies; it is present in larger 
 amount in early than in adult life, in grey than in white matter, 
 in the brain than in the spinal cord, in the spinal cord than in 
 nerves. 
 
 This is illustrated by the following tables : 
 
 TABLE 1. 
 
 INFLUENCE OF AGE ON THE PERCENTAGE OF WATER IN THE BRAIN TISSUE. * 
 
 White matter Grey matter 
 
 In foetus 87 92 
 
 Age 20-30 69 ... ... 83 
 
 Age 70-90 72 84 
 
 TABLE II. 
 
 PERCENTAGE OF WATER IN DIFFERENT PARTS OF THE NERVOUS SYSTEM OP 
 
 THE ADULT. 2 
 
 Grey matter of Brain 81-86 
 
 White matter of Brain 68-72 
 
 Brain as a whole ... ... ... ... 81 
 
 Spinal cord 68-76 
 
 Nerves 57-64 
 
 TABLE III. 
 PERCENTAGE OF WATER IN DIFFERENT PARTS OF THE NERVOUS SYSTEM.* 
 
 Grey matter of cerebrum 83 -4 
 
 White matter of cerebrum ... ... ... 69 '9 
 
 Cerebellum 79'8 
 
 Spinal cord as a whole ... 71 '6 
 
 Cervical cord ... ... ... ... ... 72'5 
 
 Dorsal cord 69'7 
 
 Lumbar cord ... ~ ... ... ... ... 72 '6 
 
 Sciatic Nerves 65'3 
 
 We thus see that water is most abundant in the grey matter,, 
 or in those regions of the nervous system where the proportion 
 of grey matter is greatest. It cannot fail to be a striking fact 
 
 1 Weisbach, Hofmanri's Lehrbiich d. Zoochemie, Wien., 1876, p. 121. 
 
 2 Table compiled from a number of analyses made by others. 
 
 3 This table gives the averages of a large number of experiments made 
 with the organs of human beings, monkeys, dogs, and cats, by myself. 
 (Journal of Physiology, 1893, vol. xv., p. 90.) 
 
6 THE CROONIAN LECTURES ON THE 
 
 that the grey matter, the region which is most active, and most 
 important, contains somewhat less than 17 per cent, of solid 
 materials. 
 
 SPECIFIC GRAVITY. 
 
 The question of the amount of water is closely related to that 
 of specific gravity. The specific gravity of the brain has been 
 the subject of researches by Bischof, Danilewski, and others, but 
 I only wish here to dwell upon one aspect of the question which 
 has interested me, and which was brought prominently before the 
 medical profession in an address on " Sex in Education," by Sir 
 James Crichton Browne, 4 some years ago. Among the differences 
 between the brains of men and women, Sir James stated that he 
 had found that the specific gravity of the female brain is less 
 than that of the male brain. It was, however, pointed out in 
 the correspondence that followed the publication of the address, 
 that this generalisation rested on very few observations, the 
 brains of two healthy men and one healthy woman having been 
 investigated. Observations on the brains of lunatics, which were 
 mainly used, can hardly be considered as likely to yield trust- 
 worthy results of what obtains in the normal state. I have 
 accordingly thought it advisable to examine the brains in a 
 larger number of cases. This has been carried out in my 
 laboratory by Mr. Gompertz, B.Sc. The details of his experi- 
 ments will be published elsewhere, A^L I shall do here is to 
 mention his main conclusion. He finds that in adult men and 
 women who suffered from no brain disease, that there are fairly 
 wide variations in both sexes, but that the average is practically 
 identical in male and female, and that there is no foundation for 
 the belief that the variations constitute a sexual difference. 
 
 I may point out that a low specific gravity of the brain does 
 not necessarily imply a poorer quality, for the part of the brain 
 which is most important and most active the grey matter has 
 a lower specific gravity than the white matter. 5 
 
 4 British Medical Journal, 1892, vol. i., p. 949. 
 
 5 This fallacy underlies a good deal of the statements made on this subject. 
 J. P. H. Boileau (Lancet, 1882, vol. ii., p. 485), for instance, draws attention, 
 in the examination he made of the brain of a highly-gifted man, not only to 
 its great weight but also to its high specific gravity. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 
 
 SOLIDS OF NERVOUS TISSUES. 
 
 But coming now to the more important subject of the solids 
 we find it is possible to divide them into the following classes : 
 
 (a) Proteids. These comprise a very considerable percentage 
 of the solids, especially in the grey matter (over 50 per cent.). 
 
 (b) Nuclein. From the nuclei of the cells. 
 
 (c) Neuro-keratin. From the supporting framework (neu- 
 roglia). 
 
 (d) Fats : including phosphorised fats (protagon and lecithin). 
 
 (e) Cerebrins or cerebrosides. Nitrogenous glucosides. 
 (/) Cholesterin. 
 
 (g) Extractives. Small quantities of numerous organic sub- 
 stances, of which creatine, xanthine, hypoxanthine, inosite, lactic 
 acid, uric acid, and urea have been identified. 
 
 (h) Gelatin. From the adherent connective tissue. 
 
 (i) Inorganic salts. Of these, alkaline pkosphates and 
 chlorides are the most abundant, but the total ash is only about 
 1 per cent. 
 
 The following table gives some typical quantitative analyses 
 which have been made of the proportion in which the principal 
 solids occur in different nervous structures : 
 
 TABLE IV. 
 
 Portion of nervous system 
 
 Proteids 
 
 Lecithin 
 
 Choles- 
 terin 
 and fat 
 
 Cerebrin 
 
 
 Salts 
 
 Grey matter of ox brain 
 (Petrowsky) 
 White matter of ox brain 
 (ibid.) 
 
 55-37 
 24-72 
 
 17-24 
 9-90 
 
 18-68 
 51-91 
 
 0-53 
 9-55 
 
 6-71 
 3-34 
 
 1-45 
 
 0-57 
 
 Spinal cord (Moleschott) 
 
 23-8 
 
 
 
 75-1 
 ^s^ 
 
 
 1-1 
 
 Human sciatic nerve 
 (Josephine Chevalier) . . 
 
 36-8 
 
 32-57 
 
 12-22 
 
 1^30 
 
 3-07 4-0 
 
 
 
 Some of the substances just mentioned require fuller notice, 
 and in particular we must consider the proteids, protagon and 
 lecithin, and the cerebrosides. 
 
 PROTEIDS OF NERVOUS TISSUES. 
 
 The large amount of proteid matter, next to the high per- 
 centage of water, is the most striking fact in the preceding table. 
 
8 
 
 THE CROONIAN LECTURES ON THE 
 
 TABLE V. 
 
 WatPr <*nlirt Percentage of 
 proteid in solids 
 
 83-467 
 
 16-533 
 
 51 
 
 69-912 
 
 30-088 
 
 33 
 
 79-809 
 
 20-191 
 
 42 
 
 71-641 
 
 28-359 
 
 31 
 
 72-529 
 
 27-471 
 
 31 
 
 69-755 
 
 30-245 
 
 28 
 
 72-639 
 
 27-361 
 
 33 
 
 65-349 
 
 38-684 
 
 29 
 
 The highest percentage is found where one would expect it, 
 namely, in the grey matter, where the protoplasmic structures, 
 the nerve-cells, occur. 
 
 The following table is a compilation from my own analyses : 
 
 Grey matter of cerebrum 
 White 
 
 Cerebellum . . 
 Spinal cord as a whole 
 Cervical cord 
 Dorsal cord . . 
 Lumbar cord 
 Sciatic nerves 
 
 This table illustrates the fact that the amount of grey matter, 
 of water, and the percentage of proteid in the solids vary directly 
 the one with the others. This is very well seen in the different 
 regions of the spinal cord. The percentage of proteid matter in 
 the white matter of the brain is a little higher than in the spinal 
 cord. This is the only exception to the general rule, and perhaps 
 may be explained by the high percentage of neuro-keratin in 
 white matter. 6 
 
 The earliest to study the nature of the proteids was 
 Petrowsky. 7 He investigated the question previous to our 
 modern ideas concerning proteids, and described them as con- 
 sisting of a globulin somewhat resembling myosin, and an albu- 
 min especially abundant in grey matter. Baumstark 8 in a more 
 recent research speaks of the chief proteid matter in nervous 
 tissue as resembling casein. There is a certain amount of truth 
 in this, for it is a nucleo-proteid. A few years later I took up the 
 matter, and the following were my chief conclusions. 9 
 
 The proteids present are three in number. They differ in 
 temperature of heat coagulation, in the readiness with which they 
 are precipitated by neutral salts, and by acetic acid ; one of them 
 
 6 The percentage of neuro-keratin is in grey matter, 0-3; in white matter, 
 2-2 to 2-9; and in nerve, 0'3 to 0-6 per cent. (Kiihne and Chittenden, ZeitscJi. 
 f. Biol., xxvi., p. 291). 
 
 Pfliiger's Archiv., vii., p. 367. 
 
 8 Zeitsch. f. physiol. Chem., ix., p. 145. 
 
 9 Journ. of Physiology, xv., p. 106. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 
 
 contains phosphorus and is a nucleo-proteid, so differing from 
 the other two, which are globulins. The most important charac- 
 ters of these proteids are the following : 
 
 (a) This proteid is a globulin ; it may conveniently be termed 
 neuro- globulin a. It is coagulated by heat at the low temperature 
 of 47, and is analogous to similar globulins which are found in 
 all cellular structures, such as cell-globulin of lymph-cells, para- 
 myosinogen or musculin of muscle, hepato-globulin a of the liver, 
 and kidney globulin. Indeed, this proteid seems to be as con- 
 stant a constituent of protoplasmic structures as the nucleo- 
 proteids are. 
 
 It is precipitated by a comparatively small percentage of such 
 neutral salts as magnesium sulphate. It is not precipitated by 
 weak acetic acid. It contains no phosphorus in its molecule. 
 
 In view of the subject of hyperpyrexia, a pathological problem 
 we shall be considering later, I would ask you to make a mental 
 note of the low coagulation temperature of this proteid. 
 
 (b) This proteid is a nucleo-proteid. It can be readily pre- 
 pared from nervous tissues by making a saline extract, but under 
 these circumstances it is mixed with the other proteids. It may, 
 however, be prepared in large quantities by precipitating an 
 aqueous extract of brain by weak acetic acid. The supply obtain- 
 able from white matter is small. 
 
 It is coagulated by heat at 56 to 60. Like globulins it is pre- 
 cipitable by saturating its solutions with neutral salts ; but more 
 salt is necessary than in the case of neuro-globulin a. 
 
 It contains 0-5 per cent, of phosphorus. 
 
 After subjection to gastric digestion, an unsoluble residue of 
 nuclein remains behind. 
 
 Dissolved in dilute sodium carbonate and injected into the 
 vascular system of rabbits it causes, like other nucleo-proteids, 
 extensive intravascular coagulation. 
 
 (c) This proteid is a globulin. It may conveniently be called 
 neuro-globulin ft, and is closely analogous to the hepato-globulin 
 ft of liver cells. It is coagulated by heat at 70 to 75 C. ; it is 
 precipitable by neutral salts, but requires complete saturation 
 with magnesium sulphate to precipitate it entirely. It is not 
 precipitable by weak acetic acid like the nucleo-proteid just 
 described, and contains no phosphorus in its molecule. 
 
 The only other research with which I am acquainted on the 
 
10 THE CROONIAN LECTURES ON THE 
 
 proteids of nervous tissues is one by P. A. Levene. 10 He has 
 particularly directed his attention to the nucleo-proteid of the 
 brain, and although he separated it out from the organ by a 
 method different from that which I employed, he was evidently 
 dealing with the same substance ; the amount of phosphorus 
 being 0*5 per cent., which is the same number I obtained. The 
 purine bases obtainable from cerebro-nucleo-proteid are guanine, 
 adenine, small quantities of xanthine, but no hypoxan thine. 
 
 PEOTAGON AND LECITHIN. 
 
 In the year 1865 Liebreich 11 separated from the brain a material 
 he termed pro logon ; he further found that when decomposed by 
 baryta-water it yields two acids stearic acid and glycero-phos- 
 phoric acid and a base called choline. 
 
 Hoppe-Seyler, and Diaconow 12 working under Hoppe-Seyler's 
 direction, denied the existence of this substance protagon, and 
 considered that it was a mere mechanical mixture of the 
 phosphorised fat called lecithin, with a nitrogenous non-phos- 
 phorised substance called cerebrin. Lecithin yields the same 
 three decomposition products that were obtained from protagon 
 by Liebreich. Diaconow's elementary analyses were, however, 
 far from convincing. 
 
 The subject in this country was taken up by Gamgee and 
 Blankenhorn 13 ; and the result of their work has been that 
 Liebreich's discovery has been fully verified. They showed 
 that protagon is a perfectly definite crystalline substance of 
 constant elementary composition. They also showed that even 
 prolonged treatment with alcohol and ether will not extract 
 lecithin from protagon, as alleged by Diaconow. When protagon 
 is digested with alkalis it yields cerebrin or cerebrins and the 
 decomposition products of lecithin. 
 
 This work has been confirmed by Baumstark, 14 Koppel, 13 and 
 Kossel and Freytag. 16 
 
 10 Archives of Neurology and Psychopathology,v. ii., p. 1-14, 1899. 
 
 11 Liebreich, Annalender Chem. u. Pharm., cxxxiv., p. 29. 
 
 12 Diaconow, Centralbl f. d. Med. Wissensch., 1868, p. 97. 
 
 13 Gamgee and Blankenhorn, Journ. of Physiology, ii. , p. 113. 
 
 14 Baumstark, Zeitch. f. physiol. Chem., ix., p. 329. 
 
 15 Zeitsch. f. Bwl, xxxi., p. 86. 
 
 16 Zeitsch. f. physiol. Chem., xvii., p. 431. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 11 
 
 Protagon is prepared by digesting brain with alcohol at 
 45 C., the extract is filtered while warm, and then cooled to C. 
 Protagon crystals mixed with cholesterin are thus deposited. 
 The cholesterin is dissolved out by ether. The protagon is then 
 collected, redissolved in warm alcohol, and allowed to recrys- 
 tallise on cooling. Its formula is C l6o H 3o8 N 5 PO 35 . 
 
 An elaborate research by Thudichum 17 led him to the con- 
 clusion that there are three groups of phosphorised substances 
 in the brain, which he termed kephalins (very soluble in ether), 
 myelins (far less soluble in ether), and lecithins (characterised 
 by their extreme instability). In each of these ill-defined groups 
 there are several members, the empirical formulae of which have 
 been calculated. 
 
 Thudichum' s work has, however, been so far confirmed by 
 that of Kossel, in that he has shown that protagon is not a single 
 substance, but that there is more than one protagon. They 
 yield either one, two or three derivatives of the cerebrin group, 
 and lecithin in addition. There are also several lecithins con- 
 taining different fatty acid radicles. : 
 
 The cerebrins are nitrogenous substances which are found in 
 large quantities in the white substance (especially in the medul- 
 lary sheaths), and also in egg-yolk, pus corpuscles, spleen cells, 
 &c. Many members of the group have been separated and 
 analysed since they were first studied by Miiller. These have 
 received various names (phrenosin, kerasin, pseudo-cerebrin, 
 &c.), but at present the subject is one which has not advanced 
 into the area of practical medicine. Suffice it to say that their 
 other name of cerebroside indicates that they are glucosides, and 
 that the sugar obtained from them has been identified as galac- 
 tose almost simultaneously in this country and iiwGermany. 18 
 
 Though these substances possess an attractiveness due to 
 the fact that they are still on the borders of an unknown 
 country, it is refreshing to turn next to the other material 
 derived from protagon, namely, lecithin, for here we have to deal 
 with a substance of which the composition is known, and the 
 decomposition products of which possess a distinct physiological 
 and pathological importance. 
 
 17 Thudichum, Report of Med. Officer of Privy Council, 1874, p. 113 et seq. 
 
 18 Brown and Morris, Proc. Cliem. Soc., London, 1889, p. 167 ; Thierfelder, 
 Zeitsch. /. physiol. Chem., xiv., p. 209. 
 
12 THE CKOON1AN LECTURES ON THE 
 
 It is a complex fat of wide distribution, being a constituent of 
 protoplasm. The tables of analyses already given show its 
 quantitative importance in nervous structures. When it is 
 decomposed, either in the laboratory or in the body, it breaks up 
 into three substances, as shown in the following equation : 
 
 -h 3H 2 = 2C I8 H 36 2 + C 3 H 9 P0 6 + C S H I5 N0 2 
 
 [lecithin] [stearic acid] [glycero- [choline] 
 
 phosphoric acid] 
 
 There are other lecithins present in smaller quantities which 
 yield other fatty acids on decomposition. To give the fore- 
 going lecithin its chemical name we must call it choline-distearyl- 
 glycero-phosphoric acid. The choline radicle is united to the 
 acid by means of the oxygen of the hydroxyl, it is therefore not 
 a salt but an ether-like combination, thus : 
 
 CH 2 0-C 17 H 35 CO 
 CHO -C I7 H 3S CO 
 CH 2 0-PO-O.C 2 H 4 
 
 H HO 
 
 The same facts can be put more simply by comparing an 
 ordinary fat with lecithin. An ordinary neutral fat such as those 
 which are found in adipose tissue or milk contains only three 
 elements, carbon, oxygen and hydrogen. Lecithin contains the 
 same three elements with nitrogen and phosphorus in addition. 
 An ordinary neutral fat on decomposition links to itself the 
 elements of water, and then splits up (is hydrolysed) into 
 glycerin and a fatty acid ; thus stearin yields stearic acid and 
 glycerin ; palmitin, palmitic acid and glycerin ; and olein, oleic 
 acid and glycerin. 
 
 Fat -f water 
 
 Fatty acid Glycerin. 
 
 Lecithin yields not only a fatty acid and glycerin, but in 
 addition to these substances it gives rise to phosphoric acid, 
 which contains all the phosphorus of the lecithin, and choline, an 
 alkaloid which contains all the nitrogen of the lecithin. 
 
 Lecithin + water 
 Glycerin Fatty acid Phosphoric acid Choline. 
 
NJI 
 
 CHEMICAL SIDE OP NERVOUS ACTIVITY 13 
 
 In this connection choline is of considerable importance, 
 because it can be readily detected, and the presence of choline 
 may be usually taken as evidence that lecithin, and so nervous 
 material generally, has undergone decomposition. Choline is an 
 ammonium base, which has the following constitution. 
 
 (CH 3 ) 3 
 CH 2 -CH 2 OH 
 
 (OH 
 
 Its name was originally given to it because it was first 
 separated out from the lecithin of the bile ; but its chemical 
 name is trimethyl-oxyethyl-ammoniuin hydroxide. It was at one 
 time thought to be identical with the base neurine which Liebreich 
 separated from nervous tissues, and the two are closely related, 
 choline readily becoming converted into neurine under the 
 influence of certain bacterial agencies. Neurine has also been 
 obtained by Brieger from the putrefactive decomposition of flesh, 
 Neurine only differs from choline by two atoms of hydrogen and 
 one of oxygen ; and its structure 
 
 HO.N.(CH 3 ) 3 0,H 3 
 
 justifies its chemical name, which is trimethyl-vinyl-ammonium 
 hydroxide. These two alkaloids are also closely related to two 
 others, namely, betaine, the non-toxic alkaloid of the common 
 beet, and muscarine, the highly poisonous alkaloid of the toad- 
 stool, Agaricus muscariiLs. 
 
 It will be beside my present purpose if I pursue this aspect 
 of the subject more fully ; the list of chemical substances I have 
 given is a long one, and no doubt there is considerable theoretical 
 interest attaching to many of them. I have purposely selected 
 the proteids and the phosphorised fat for fuller consideration 
 because they are the most abundant, and, so far as our present 
 knowledge goes, the most important substances which are present. 
 
 THE CEKEBROSPINAL FLUID. 
 
 Any account of the chemical structure of the brain would be 
 incomplete without some reference to the cerebrospinal fluid, 
 and I propose to conclude my first lecture by a brief description 
 of this remarkable fluid. 
 
 Most of our knowledge of the cerebrospinal fluid has been 
 derived from an examination of the contents of meningoceles, and 
 
14 THE CEOONIAN LECTURES ON THE 
 
 in cases of hydrocephalus. The fluid removed by the first 
 tapping at all events may be regarded as fairly normal. A few 
 years ago, however, I had the opportunity of examining the fluid 
 from a remarkable case which was under the care of Dr. St. Glair 
 Thomson. The patient was a young woman who had for years 
 suffered from continuous dripping from the nose ; this was not 
 amenable to any treatment. At first it was thought to be a case 
 of nasal hydrorrhoea, but certain characters in the affection con- 
 vinced the observer that this could not be so, and that the fluid, 
 which dropped from one nostril only, was cerebrospinal fluid. 
 This was supported by the results of the chemical examination 
 of the fluid. 
 
 The escape of cerebrospinal fluid from the nose has long 
 been known to follow traumatic injury to the cribriform plate of 
 the ethmoid bone, but the possibility of its spontaneous escape 
 from the nose does not appear to have been fully established 
 before the present instance. However, considerable research 
 into the literature of the subject has shown that there are 
 several cases recorded in which, though no history of injury 
 existed, the flow of fluid from the nose was of such a character 
 that they must have been similar to the present case, although in 
 the majority of instances the true nature of the fluid escaped 
 observation. Many of these patients exhibited cerebral symp- 
 toms in the course of the disease, and some ultimately died from 
 inflammation of the cerebral meninges, which had probably 
 spread from the nose through some opening in the bony lamina- 
 that normally separates the cranial and nasal cavities. 19 
 
 The first enquiries we instituted in Dr. Thomson's case 
 related to the quantity of fluid formed. One portion, collected 
 by the patient herself in the course of an hour, measured 4 cc. 
 Another portion, collected under the supervision of Dr. Thomson 
 in ten minutes, measured 3'9 cc. 
 
 If the first portion is taken as a measure of the rate of 
 secretion, the amount formed in the day will be 96 cc. Taking, 
 however, the second observation as being more accurate, the 
 
 19 " Observations on the Cerebrospinal Fluid in the Human Subject," by 
 St. Glair Thomson, M.D., Leonard Hill, M.B., F.R.S., and W. D. Halliburton,. 
 M.D., F.R.S., Proc. Royal Society, vol. Ixiv., p. 343. 
 
 A full account of the case is given in Dr. Thomson's book, " The Cere- 
 brospinal Fluid." Cassell and Co., 1899. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 15 
 
 amount formed in the twenty-four hours will be over half a litre 
 (561/6 cc.). It is possible that this estimate is too high, as 
 doubtless the patient, being under the observation of a physician, 
 would be somewhat excited, and the consequent alteration of the 
 circulation would, as we shall immediately see, cause the flow 
 to become more abundant. 
 
 In a monograph on the cerebral circulation' 20 Leonard Hill put 
 forward the view that the rate of secretion of the cerebrospinal 
 fluid, when the cranio-vertebral cavity is opened, depends directly 
 on the difference between the pressure in the cerebral capillaries 
 and that of the atmosphere. At the same time it was shown that 
 cerebral capillary pressure varies directly and absolutely with 
 vena cava pressure. Thus the cerebral capillary pressure can be 
 raised with great ease by any agency which causes a rise of 
 pressure in the vena cava or cerebral veins. On the other hand, 
 cerebral capillary pressure varies directly, but only proportion- 
 ately, with aortic pressure, for between the aorta and the capil- 
 laries there lies the peripheral resistance. 
 
 It follows from the above that the easiest methods of raising 
 the cerebral capillary pressure in man are : (a) By compression 
 of the abdomen, (b) By the assumption of the horizontal 
 posture. In this position, however, the rise of venous pressure 
 may be compensated by the fall of arterial pressure, which 
 normally occurs when the body is at rest. This is, no doubt, 
 the case during sleep, (c) By straining or forced expiratory 
 effort, with the glottis closed. 
 
 By all these methods the vena cava pressure is considerably 
 raised ; and by the last method the venous inlets into the thorax 
 may be completely blocked, and the pressure in the cerebral 
 capillaries raised to something like aortic pressure. 
 
 It is true that by such a forced expiratory effort the aortic 
 pressure is lowered. Nevertheless, the total effect on capillary 
 pressure is a very great rise, for a fall of aortic pressure of 25 mm. 
 of mercury produces a fall in cerebral capillary pressure of less 
 than 5 mm. of mercury, while a rise of vena cava pressure of 
 25 mm. of mercury produces a rise of cerebral capillary pressure 
 of 25 mm. Hg. 
 
 20 " The Physiology and Pathology of the Cerebral Circulation," by Leonard 
 Hill. London Messrs. Churchill, 1896. 
 
16 THE CBOONIAN LECTURES ON THE 
 
 Dr. Thomson's case gave us a unique opportunity of testing 
 the correctness of these views on the living human subject, and 
 our experiments entirely confirm them. As will be seen from the 
 following figures, the flow of cerebrospinal fluid is accelerated by 
 all those circumstances which raise the cerebral capillary pressure. 
 The increase in flow is, moreover, accompanied by a decrease in 
 the percentage of solid matter. 
 
 The fluid passed while the patient was making forced expira- 
 tory efforts was nearly double in quantity that which flowed 
 while she was sitting quietly. Abdominal compression also 
 raised the rate of flow, by increasing the vena cava pressure and 
 so leading to increase of the cerebral capillary pressure. In all 
 cases increase of volume is accompanied with fall in the percentage 
 of solids in the fluid. 
 
 The following table illustrates these points : 
 TABLE VI. 
 
 n -,.,. . .. . Amount of fluid collected Percentage of 
 
 Condition of patient in ten minuteg solidg - n gg flu - d 
 
 1. Sitting quietly 2-378" cc. .. .. 1-1 
 
 2. During straining .. .. 3-912 cc 0'43 
 
 1. Sitting quietly 2-188 cc 1-14 
 
 2. Abdomen compressed .. .. 3 '009 cc 0-68 
 
 1. Sitting upright .. ,. .. 1-670 cc I'll 
 
 2. Lying down 3-245 cc 1-03 
 
 Cavazzani, 21 from experiments on dogs, found that the cerebro- 
 spinal fluid collected in the morning was more alkaline than in the 
 evening, and contained more solid residue. He considers that 
 this is related to the activity of the nervous system, and that it 
 confirms Obersteiner's theory of sleep. He obtained correspond- 
 ing results in the case of a man with traumatic fistula of the 
 frontal bone. 
 
 We considered it worth while to repeat this observation. 
 
 The qualitative examination of the fluid collected first thing 
 on several mornings gave the same results as that of specimens 
 collected the last thing in the evening. Both were distinctly 
 alkaline, but no estimation of the relative alkalinity was made. 
 The following table gives in percentages the results of the 
 quantitative analyses : 
 
 21 "Sul Liquido Cerebrospinale," La Riforma Medica, Anno VIII., 1892, 
 vol. ii., p. 591. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 17 
 
 Morning fluid Evening fluid 
 
 Water 99-004 .. .. 99-027 
 
 Solids ,. 0-996 .. .. 0-973 
 
 Organic solids . . . . 0-118 . . . . 100 
 
 Inorganic solids .. .. 0'878 .. .. 0*873 
 
 The evening fluid is thus slightly poorer in both classes of 
 constituents than that of the morning ; the difference is chiefly 
 due to an alteration in the organic solids. This is just what we 
 should expect, as the decreased capillary pressure during sleep 
 would lessen the rate of exudation of water. Without committing 
 ourselves to any theory on nervous activity or sleep, we may say 
 that our experiments confirm those of Cavazzani. 
 
 All our experiments, therefore, show the close correspondence 
 between the amount of the fluid and the height of cerebral 
 capillary pressure. But in spite of this, cerebrospinal fluid is 
 not a simple pressure exudation from the blood. The idea that it 
 is a secretion was first propounded by Carl Schmidt many years 
 ago, long before the birth of Heidenhain's theory that all lymph 
 must be regarded as a secretion, in the formation of which the 
 endothelial cells of the capillaries play a selective action. 
 
 Schmidt propounded his doctrine on the strength of his 
 analyses of the saline constituents of the fluid ; he stated that 
 potassium salts are more abundant than those of sodium. But 
 this has not been confirmed by subsequent investigators. Thus 
 Yvon 22 gives the following numbers, NaCl 7-098, and KC1 033 
 per 1,000. F. Miiller 23 gives the relationship of NaCl to KC1 as 
 21*5 : 1. My own figures 24 in cases of meningocele show in 100 
 parts of chlorides that 95*15 consist of sodium chloride, and 4-85 
 of potassium chloride. 
 
 The amount and proportions of the salts are thus about the 
 same as in blood, lymph, and transudations generally. 
 
 But examination of the organic solids shows Schmidt's con- 
 tention that cerebrospinal fluid is a secretion to be correct, 
 though the grounds on which he supported his idea are in- 
 correct. 
 
 The fluid stands apart from all other similar fluids in the 
 following particulars : 
 
 22 Journ. de Pharm. et de Chemie, fourth series, xxvi., p. 240, 1877. 
 
 23 Mittheil. a. d. Wiirzburger med. Klinik, i., p. 267. 
 
 24 Journ. of Physiology, x. , p. 232. 
 
 2 
 
18 THE CROONIAN LECTURES ON THE 
 
 (1) Its clear watery character. 
 
 (2) Its low specific gravity, 1,004 to 1,007. 
 
 (3) It only contains a trace of proteid ; the characters of this 
 are those of globulin, whilst in some cases a small admixture of 
 proteose is present. Fibrinogen and albumin are absent. 
 
 (4) The presence in it of a substance which reduces Fehling's 
 solution, but does not ferment with yeast, nor does it give any 
 osazone crystals. The substance is therefore not sugar. 25 It is 
 possibly an aromatic substance, allied to pyrocatechin, but this 
 requires renewed investigation. 
 
 The following analyses (in parts per 1,000) of the fluid from 
 spina bifida cases may be next given 26 : 
 
 TABLE VII. 
 
 In parts per 1,000 Case 1 Case 2 Case 3 
 
 Water .. . . 989 '75 .. 989-877 .. 991-658 
 
 Solids .. .. 10-25 .. 10-123 .. 8 -342 
 
 Proteids .. .. 0-842 .. 1-602 .. 0-199 
 
 Extractives | 9>626 ( 0-631 .. 3'028 
 
 Salts I 7-890 .. 5-115 
 
 The percentage of organic solids is thus as a rule a little higher 
 than in the absolutely normal fluid. In cases of hydrocephalus 
 the percentage of solids is rather greater (see next table). 
 
 TABLE VIII. 
 
 In parts per 1000 Case 1 Case 2 Case 3 
 
 Water 986-78 .. 984-59 .. 980-77 
 
 Solids 13-22 .. 15-41 .. 19-23 
 
 Proteids and extractives .. 3'74 .. 6'49 .. 11 -35 
 
 Salts ..'..; .. .. 9-48 .. 8-92 .. 7'88 
 
 In cases of chronic hydrocephalus, the fluid removed by the 
 first tapping has the normal qualitative characteristics of cerebro- 
 spinal fluid ; but that removed by subsequent tappings resembles 
 a dilute transudation from the blood, and if inflammation super- 
 venes this becomes more marked ; the proteids become more 
 abundant, and resemble those found in blood and lymph ; the 
 
 25 Nawratski, in a recent paper (Zeitsch. f. physiol. Chem., xxiii., p. 523. 
 1897), has affirmed, principally from observations on the cerebrospinal fluid 
 of the calf, that the reducing substance is dextrose. This is directly contrary 
 to the observations of all other writers on the subject, and to my own 
 experiments. 
 
 28 W. D. Halliburton, u Report of Spina Bifida Committee," vol. xviii. of 
 Clin. Soc. Transactions. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 19 
 
 amount of reducing substance increases, and is here probably 
 mixed with sugar. This is illustrated in the following table : 
 
 TABLE IX. 
 CASE OP CHRONIC HYDROCEPHALUS. 
 
 Specific Percentage of Reducing 
 
 gravity proteids substance 
 
 First tapping . . 1006 . . 0-045 . . Traces 
 
 Second tapping . . 1010 . . 0-069 . . Fairly abundant 
 
 Third tapping . . 1010 . . 0-272 . . More abundant 
 
 Returning now for a moment to normal cerebrospinal fluid, 
 we find that its osmotic relationships are different from those of 
 ordinary lymph. 
 
 Thus Zanier 27 finds in the ox that the fluid is hypertonic 
 compared to the serum of the same animal. Widal, Sicard, and 
 Ravant 28 arrived at the same result by the cryoscopic method. 
 This character separates it from other serous fluids, and various 
 drugs pass from the cerebrospinal fluid into the blood. 
 
 M. Lewandowsky 29 has performed somewhat similar experi- 
 ments ; he regards the fluid as a specific product of the brain, 
 and only to a small extent as a simple transudation from the 
 blood. 
 
 The experiments of F. Ransom 30 with tetanus toxin and anti- 
 toxin show that these organic materials will pass from the 
 cerebrospinal fluid to the blood, though they pass in the opposite 
 direction from the blood to the lymph. 
 
 It is an interesting question whether the fluid has the same 
 composition in all parts, for the fluid has a double origin. It is 
 found in the lymph channels and spaces of the brain and cord 
 tissue, and the perivascular lymphatics have been shown to open 
 into the subarachnoid space. In the second place, it is found in 
 the cerebrospinal cavity (ventricles of brain and central canal of 
 cord), and it can hardly be doubted that it is here formed largely 
 by the secretory epithelial cells which cover the choroid plexuses. 81 
 We can only surmise that this double method of formation may 
 
 27 Centralbl.f. PhysioL, x., 1896. 
 
 a La Presse medicale, October 24, 1900, p. 128. 
 
 29 Zeit. klin. Med., xl., p. 480. 
 
 30 Zeitsch. /. physiol. Chem., 1900, xxxi. 
 
 31 See article on Meningitis, by Dr. Lees and Sir T. Barlow, in Allbutt's 
 " System of Medicine." 
 
20 THE CKOONIAN LECTURES ON THE 
 
 imply a difference in the composition of the fluid formed. The 
 fluid as usually examined must be a mixture of the two, and 1 
 cannot see that we have at present any certain method of 
 collecting the two fluids separately. 
 
 I will conclude with one more question, and that is, whether 
 choline occurs in normal cerebrospinal fluid. The importance 
 of this question arises from the fact that choline is a substance 
 which leads itself readily to detection, and its presence is a 
 valuable indication of a break down of nervous tissue. In a fluid 
 which plays the part of a lymph, we naturally look for the 
 products of disintegration of any tissue. Mott and I have shown 
 that in diseased conditions in which the katabolic side of nervous 
 action is preponderant, choline is found in great abundance. 
 This is a point I shall have to dwell upon more fully later. For 
 the present it is sufficient to say that in the normal fluid so 
 little is present that it may be regarded as absent .for all prac- 
 tical purposes. Still it is present. This Gumprechl 32 has shown 
 to be the case ; he worked with larger quantities of fluid than 
 were used by Mott and myself. Although the quantity in the 
 normal fluid is so small, it is not without interest, for it fur- 
 nishes evidence that in the metabolism of the nervous tissues 
 lecithin as well as proteid is in a condition of unstable chemical 
 equilibrium. 
 
 82 Verhandl. des Congr. /. innere Med., Wiesbaden, 1900, p.p. 326-348. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 21 
 
 LECTUEE II. 
 METABOLISM IN NERVOUS TISSUES. 
 
 IN my first lecture I dwelt upon the general composition of 
 nervous structures, and in addition to giving you a long list of 
 the chemical substances found there, with tables of quantitative 
 analyses, devoted some time to a description of the proteids, and 
 phosphorised constituents of nervous material. 
 
 But living material is never at one moment the same chemi- 
 cally as it was the moment before, or will be the moment after. 
 This condition of unstable chemical equilibrium, indicative of 
 continual and continuous intra- molecular re-arrangements, is 
 summed up by the convenient word metabolism; the assimila- 
 tive changes which lead to the building up of protoplasm and 
 the repair of waste is generally termed anabolism, while the 
 contrary phase, the disintegrative, which is the result of the 
 wear and tear associated with activity, is called katabolisrn. 
 
 I propose to ask you to-day to follow me in the enquiry as 
 to the evidence we possess of metabolic activity in nervous tissues. 
 This will involve the discussion of such questions as fatigue and 
 sleep. I am afraid we shall meet with considerable disappoint- 
 ment in the answers we shall be able to furnish to our enquiries, 
 for it is in this part of our subject that our knowledge is 
 scantiest. 
 
 To ascertain the chemical composition of the brain when it 
 is dead is a task of some difficulty, but it is easy when compared 
 with the endeavour to determine what chemical changes it 
 undergoes while it is alive. 
 
 We are only on the threshold of our chemical enquiries ; still 
 the time cannot be far distant when we shall have crossed it 
 and opened the door to more certain knowledge. We shall find 
 here that the experiments made for us by nature, which we call 
 
22 THE CBOONIAN LECTURES ON THE 
 
 diseases, will come to our aid, for in pathological conditions we 
 have not the nicely balanced equilibrium between anabolism and 
 katabolism which characterises the physiological state, but as a 
 rule the katabolic side predominates and so we are enabled to 
 grasp it. 
 
 Very often for the purposes of teaching and illustration we 
 compare the nervous system to a telegraphic system penetrating 
 to every part of a country and serving for the regulation and 
 ordering of the various occurrences which take place there. 
 Messages fly to and from distant parts, and are received, co- 
 ordinate'd or started at central offices, which we may compare 
 to the groups of nerve-cells we call nerve-centres. In such a 
 telegraphic system, the most active parts are the offices ; it is 
 there we look for evidence of action in the shape of fatigue in 
 the operators, or wear and tear of instruments. The wires are 
 comparatively speaking passive transmitters; they undergo but 
 little change and do not manifest signs of fatigue. 
 
 So it is in the nervous system ; the signs of action are to be 
 found in the beginnings and endings of the nerve-fibres, the cells 
 of brain and cord, and the end organs in muscle and other 
 peripheral structures. Any evidence of fatigue in the more 
 passive transmitters, the nerve-fibres, is very difficult to discover. 
 This coincides with the arrangements of the vascular supply of 
 such parts. The nerve-centres are richly supplied with blood- 
 vessels, which furnish them with an abundant supply of nutrient 
 material. Cerebral anaemia 1 rapidly produces pathological 
 changes in the nerve-cells, and death quickly supervenes. But 
 in a nerve the blood-vessels are comparatively insignificant, and 
 a nerve can be removed from the body, and be made to manifest 
 activity for many hours subsequently. 
 
 The necessity for oxygen, and the fact that it is used up 
 during the activity of the brain, can be very strikingly demon- 
 strated by the experiment which Mr. Leonard Hill has performed 
 with the help of methylene blue. Ehrlich was the first to show 
 that if a solution of this pigment is injected into the blood stream 
 of an animal the blood is rendered blue, but the organs, especially 
 those which, like glandular organs, are in a state of activity, are 
 
 1 For recent work on this subject see Leonard Hill, F.R.S., Phil. Trans- 
 actions of the Royal Society, 1900, vol. B., 189, p. 69. 
 
CHEMICAL SIDE OP NERVOUS ACTIVITY 23 
 
 colourless. On exposure to oxygen after the organs are removed 
 from the body, they also become blue. The meaning of this is 
 the seat of oxidation is in the tissues and not in the blood. 
 Though methylene blue holds its oxygen more firmly than 
 oxyhaemoglobin does, the tissues are nevertheless able to take 
 oxygen from it and form a colourless reduction product ; but 
 after the tissues are removed from the body and consequently 
 are losing this vital avidity for oxygen, they become blue once 
 more on exposure to the atmosphere. 
 
 Now, in an anaesthetised animal the brain is inactive, and the 
 brain, like the blood, has a blue tint. If, however, a spot of the 
 cerebral surface is stimulated that part of the brain is thrown into 
 action, oxygen is used up, and the methylene blue is reduced, and 
 in consequence that area of the brain loses its blue colour. If 
 the animal is so deeply narcotised that the brain does not dis- 
 charge an impulse, the part stimulated remains blue. 
 
 In any plan of research on changes in nerve we must be 
 largely guided by what is already known of the tissue to which it 
 is so closely related, namely, muscle. 
 
 When a muscle is active, the changes it undergoes are 
 numerous and easy to detect. The naked eye can see its shorten- 
 ing; the microscope reveals changes in its constituent sarcous 
 elements. The production of heat is so prominent that a tem- 
 porary rise of temperature can be ascertained to occur even with 
 such a rough instrument as a thermometer, though for the finer 
 changes in the temperature of small muscles a thermopile is 
 necessary. Accompanying these manifestations of a transforma- 
 tion of energy, the galvanometer shows us a variation in its 
 electrical condition ; and the basis of all the other changes is the 
 sudden and massive increase of its normal chemical tone. Oxygen 
 is used up, carbonic acid is given off in large amount, and the 
 reaction of the muscle on prolonged activity becomes acid ; this 
 acidity is in part due to the formation of acid phosphates, and in 
 part to the production of sarco-lactic acid. 
 
 Turning to nervous tissues, what a contrast we have. When 
 active, no change is visible to the highest powers of the micro- 
 scope; the refractive index of the axis cylinder remains unaltered; 2 
 the most delicate thermopile fails to detect any rise of tempera- 
 
 * Gro8e, Pfliiger's Archiv., xlvi., p. 56. 
 
24 THE CROONIAN LECTURES ON THE 
 
 ture, and the chemical changes which occur are proved to take 
 place rather by circumstantial than by direct evidence. The only 
 change in a nerve which can be detected by physical means is the 
 electrical variation. 
 
 The chemical changes that occur on the death of a muscle are 
 in part an exaggeration of those which take place when it is active 
 during life. This is a guide to us when we seek to determine the 
 corresponding facts in nerve. Eolleston 3 showed that in nerve 
 there is on its death a rise of temperature. Now this can only be 
 due to increased chemical action, and probably of the same kind 
 as, though greater in degree than, that which occurs during life. 
 Moreover nervous tissues become acid when they die. 
 
 But in order to systematise the description of these changes, 
 it will be best to consider them under the following headings : 
 
 (1) The reaction of nervous tissue. 
 
 (SJ) The hypothetical production of carbonic dioxide during the 
 activity of nerve. 
 
 (3) Evidence of metabolic activity in nervous structures 
 derived from the examination of cerebrospinal fluid, and saline 
 extracts of nervous tissues. 
 
 (1) EEACTION OF NERVOUS TISSUES. 
 
 Heidenhain 4 and Gscheidlen 5 both state that the normal 
 reaction of the axis-cylinder is alkaline ; but on death or on long- 
 continued activity the reaction becomes acid. They further state 
 that the grey matter is acid even during life. O. Langendorff 6 
 found the reaction of the central nervous system alkaline during 
 life ; the alkalinity rapidly diminishes after death, or on stoppage 
 of the circulation. S. Moleschott and Battistini 7 found both 
 central and peripheral portions of the nervous system acid, 
 especially the grey matter ; this was increased by activity. 
 
 I am convinced that these conflicting statements are in part 
 due to the fact that the nervous structures in question were not 
 
 3 Journal of Physiology, xi. , p. 208. 
 
 4 CentralU.f. d. med. Wiss., 1868, p. 833. 
 
 5 Pfliiger's Archiv., viii., p. 171. 
 
 6 Neurol. Centralbl, 1885, No. 14. Centralbl. f. d. med. Wiss., 1886, 
 No. 25. 
 
 7 Arch. ital. debioL, viii., p. 90. Chem. Centr.-BL, 1887, p. 1224. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 25 
 
 always examined in the perfectly fresh condition, and they may 
 also be partly explained by the use of different indicators of 
 acidity by the various observers. 
 
 In my own work, I have found in animals that the fresh 
 tissues are invariably alkaline, but on exposure they become 
 rapidly acid, especially the grey matter. In the human brains I 
 received from the post-mortem room the reaction of the grey 
 matter was always, and of the white matter often, acid to litmus. 
 This I attribute to changes after death, for at least twenty-four 
 hours had always elapsed since death. The acidity is due to 
 lactic acid ; but according to Miiller and Gscheidlen it is not 
 sarco-lactic acid but the fermentation lactic acid. Miiller also 
 obtained traces of formic acid. 
 
 In order to test the question of whether acidity* develops on 
 activity, Dr. Brodie and I have been recently investigating what 
 occurs in a non-medullated nerve. This appeared to us the best 
 means of attacking the problem, for the possibly masking effect of 
 a large mass of myelin would then be absent. The splenic nerves 
 of the dog, which are large and easily dissected out, were used, 
 but we found that after faradisation for six hours the reaction 
 never became acid. 
 
 (2) THE HYPOTHETICAL PRODUCTION OF CARBON DIOXIDE DURING 
 THE ACTIVITY OF NERVE. 
 
 This is an interesting branch of the subject, which we owe to 
 Dr. Waller. Dr. Waller uses as his object of attack isolated 
 nerves, usually the sciatic nerves of frogs. He stimulates them 
 in the usual way by induction shocks, and he takes their elec- 
 trical response as his guide to their activity. He has in this 
 way studied the influence of numerous reagents and drugs upon 
 nerve, and the presence and extent, or the absence of the 
 galvanometric answer show whether any particular reagent 
 increases, diminishes, or annuls nervous action. Among the 
 reagents which he thus investigated carbonic acid is one, and 
 his results with this gas are most instructive. Large doses of 
 carbonic acid act like an anaesthetic, and completely abolish 
 the electrical response, but the nerve soon recovers when the 
 poisonous gas is replaced by air. Very small doses of carbonic 
 acid increase its activity, and the swing of the galvanometer 
 
26 THE CROONIAN LECTURES ON THE 
 
 needle is increased when the nerve is thrown into action. A 
 nerve thus forms a very delicate test object for this gas, far more 
 delicate, in fact, than most chemical reactions are. When a 
 nerve is excited to activity the electrical responses improve, just 
 as when a muscle is made to undergo a succession of contrac- 
 tions the beneficial effect of contraction manifests itself by what 
 is technically called the " staircase phenomenon." This bene- 
 ficial effect of previous action is exactly similar to what is 
 produced by minute doses of carbonic acid gas, and Dr. Waller 
 argues from his experiments that they prove what cannot be 
 directly tested by the rougher methods of chemical analysis, 
 namely, that activity is associated with the discharge of carbon 
 dioxide. I shall have to return to this question in our subse- 
 quent discussion of fatigue. 
 
 (3) EVIDENCE OP METABOLIC ACTIVITY IN NERVOUS STRUCTURES 
 DERIVED FROM THE EXAMINATION OF CEREBROSPINAL FLUID 
 AND OF SALINE EXTRACTS OF NERVOUS TISSUES. 
 
 We are so accustomed to associate the word metabolism with 
 the activity of the proteid constituents of protoplasm, that we 
 are sometimes apt to forget that other materials frequently 
 exhibit a similar alternate or simultaneous series of anabolic 
 and katabolic phases. In nervous structures this is particularly 
 true for the complex phosphorised molecules of protagon. Gum- 
 precht has shown that perfectly normal cerebrospinal fluid 
 contains minimal traces of choline, a substance derived from the 
 decomposition of lecithin, the main constituent of protagon. This 
 trace of choline represents the small temporary balance on the 
 wrong side of the account. Even under normal physiological 
 conditions, the products of katabolism can be detected ; this 
 becomes much more pronounced in diseased conditions. This 
 point I am reserving for fuller study in my next lecture. Exactly 
 similar evidence is obtained by making saline extracts of perfectly 
 fresh nervous tissues. Violent reagents which break up the 
 nervous tissues will naturally lead to the appearance of large 
 quantities of choline in the extract mixed with numerous other 
 substances. But physiological saline solution, the most harmless 
 of all reagents, will even at room temperature extract choline 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 27 
 
 from perfectly fresh tissues in sufficient quantities to render its 
 detection by both chemical and physiological tests an easy task 
 (see figs. 12 and 13). It is mixed in these extracts with other 
 materials, some of which are basic, but these have not been 
 accurately identified. The presence of choline in such extracts 
 indicates that in the tissues some of the protagon has undergone 
 katabolic changes, and so we have a very positive sign of chemical 
 activity in the living tissues. In addition to this fact there is 
 a further one, namely that the most active part of the nervous 
 system, the grey matter yields most choline to solvents. 8 
 
 FATIGUE. 
 
 Experimental methods have shown that in a muscle-nerve 
 preparation, fatigue is due to the accumulation of the products 
 of muscular activity, and that it may be artificially induced by 
 irrigating such a preparation with a dilute solution of sarcolactic 
 acid, and removed by neutralising this with salt solution contain- 
 ing a trace of alkali. It has further been shown that the 
 muscular fibres are not to any great extent the seat of fatigue, 
 and that the nerve-fibres are practically inexhaustible. By a 
 process of exclusion the seat of exhaustion has thus been localised 
 in the intramuscular nerve-endings. When a muscle is fatigued 
 in the intact body, there is, however, another factor to be con- 
 sidered beyond the mere local poisoning of the end-plates. This 
 is the effect of the products of muscular katabolism passing into 
 the circulation and poisoning the central nervous system. Mosso, 
 by the use of the instrument he calls the ergograph, has demon- 
 strated that the fatigue products cause most of their injurious 
 effects by acting on the central nervous system and diminishing 
 its power of sending out impulses. Moreover, the introduction 
 
 8 That this matter is attracting considerable attention just now is shown 
 by the numerous researches published during the last year or two. In 
 addition to my own paper on the "Physiological Effects of Extracts of 
 Nervous Tissues," Journ. of Physiology, xxvi., p. 229, the following may be 
 mentioned: Cleghorn, American Journ. of Physiol., ii., p. 471; Journ. of the 
 Boston Society of Medical Sciences, iv., p. 289, 1900; Osborne and Vincent, 
 Journ. of Physiology, xxv., p. 283 ; Hunt, Proc. Amer. Physiol. Soc., 1899 ; Gum- 
 precht, loc. cit. ; Gulewitsch, Zeit. physiol. Chem., xxvii., p. 50. All these 
 observers agree on the presence of choline, though some doubt whether it 
 is the most important substance which goes into solution. 
 
28 THE CROONIAN LECTURES ON THE 
 
 of the blood of a fatigued animal into the cerebral circulation of 
 a normal one will give rise in the latter to all the symptoms of 
 fatigue. The blood still remains alkaline ; the toxic material 
 cannot therefore be free lactic acid, and lactates do not produce 
 the effect. Mosso has put forward the theory that the poisonous 
 substance is basic in nature, but we have really no accurate 
 knowledge of its chemical nature. 
 
 Among these facts, the most striking is the non-fatiguability 
 of nerve-fibres. This does not mean that the nerve-fibres undergo 
 no metabolic changes when transmitting a nerve impulse. It 
 means that the change is so slight, and the possibilities of repair 
 so great, that fatigue in the usual acceptation of the term cannot 
 be demonstrated. This is an illustration of the wonderfully 
 economic way in which Nature often works. 
 
 That a change does occur in a nerve-fibre is evidenced by the 
 electrical variation it undergoes and which can be detected by 
 the galvanometer or the electrometer. Further, we have already 
 seen Dr. Waller believes he has shown that carbonic acid is 
 evolved by the axis cylinder. How, then, can we account for 
 the fact that fatigue cannot be shown to occur ? To meet this 
 difficulty Waller has tentatively suggested a most ingenious 
 explanation, which it will be well to give in his own words. 9 
 He says: "I wonder does this carbonic acid become altogether 
 dissipated ; may it not perhaps be reinvolved in some storage 
 combination, as the nerve-fat perhaps, that is so prominent a 
 constituent of fully evolved nerve. Such nerve consists of 
 proteid axis and fatty sheath; the axis which is the offshoot 
 of a nerve-cell is the specially conductile part, the sheath is a 
 developmental appendix, not directly connected with any nerve- 
 cell. Yet, cut the nerve, and sheath as well as axis undergo 
 Wallerian degeneration, which is evident proof of a functional 
 commerce between sheath and axis. You have seen further that 
 such nerve is inexhaustible, yet that it exhibits very clear 
 symptoms of chemical change after action. All these things to 
 my mind reconcile themselves with the notion that the active 
 grey axis both lays down and uses up its own fatty sheath, and 
 that it is inexhaustible not because there is little or no expendi- 
 ture, but because there is an ample re -supply." 
 
 9 "Lectures on Physiology," First Series, "Animal Electricity," 1897, 
 p. 70. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 29 
 
 A year or two after these words were written Miss Sowton, 10 
 at Dr. Waller's suggestion, undertook a piece of work in order to 
 test the truth of this hypothesis. If the absence of fatigue is 
 due to the presence of the fatty sheath, fatigue ought to be 
 demonstrable in nerve- fibres in which the fatty sheath is absent. 
 She selected the olfactory nerve of the pike as the non-medullated 
 nerve with which to try the experiment, and her results confirmed 
 Dr. Waller's expectation ; the galvanometric replies of the nerve 
 become somewhat feebler after repeated stimulation. 
 
 It appeared to me advisable to test the question in another 
 way. Some doubt has recently been cast on the trustworthiness 
 of the electrical response as a sign of nervous activity. 11 I do not 
 pretend to be able to pronounce an opinion on this subject, but as 
 the doubt has arisen, the greater becomes the necessity for a fresh 
 method of attacking the problem. The splenic nerves appeared 
 to be the rnosb convenient large bundles of non-medullated fibres 
 for the purpose. Dr. T. G. Brodie has been associated with me 
 in carrying out the investigation. A dog is anaesthetised with 
 morphine and A.C.E. mixture, the abdomen opened, the spleen 
 exposed, and the splenic nerves which lie by the side of the 
 main splenic artery are laid bare. It is quite easy to dissect out 
 a length of nerve sufficient for the experiment (l.| to 2 inches). 
 The nerve is then cut as far from the spleen as possible, and the 
 spleen is enclosed in an oncometer, similar to that employed by 
 Schafer in his work on the spleen. 12 On stimulating the nerve 
 with a weak faradic current the organ contracts, and the record- 
 ing lever falls. The diminution of the size of the spleen is quite 
 visible to the naked eye, however, without the use of any appa- 
 ratus. The next thing to do is to put a block on the course of 
 the nerve, which will prevent the nerve impulses from reaching 
 the spleen. Here we met with some difficulty. Curare and 
 atropine are both ineffective ; the constant current has a great 
 disadvantage ; non-medullated nerves are so much affected that 
 very feeble constant currents (one-third of a Danieil cell) will 
 completely block the transmission of impulses, and not only that, 
 
 10 Proc. Royal Society, vol. Ixvi., p. 379, 1900. 
 
 11 See Professor Gotch's article " Nerve " in Schafer's Text-book of 
 Physiology. 
 
 12 Schafer and Moore, Jcurn. of Physiology, xx., p. 1. 
 
30 
 
 THE CROONIAN LECTURES ON THE 
 
 but the nerve remains blocked after the current is removed. 
 After the current has been allowed to flow for two minutes the 
 nerve remains impassable to nerve-impulses for an hour or more, 
 and then slowly recovers. If, therefore, faradic excitation of the 
 nerve is kept up all this time and fails to excite the contraction 
 of the spleen after the removal of the constant current, it is 
 impossible to say whether this is due to fatigue of the nerve- 
 fibres on the proximal side of the block, or whether it may not 
 be due to the fact that the block created by the constant current 
 is still effective. 
 
 G.P. 
 
 FIG. 1. Apparatus for obtaining splenic curves, s, spleen in oncometer 
 o, which is made of gutta percha, and covered with a glass plate (G.P.) luted 
 on with vaseline. M is the splenic mesentery containing vessels and nerves ; 
 this passes through a slit in the base of the oncometer and is made air-tight 
 with vaseline. The oncometer is connected to the flexible bellows (B) by the 
 india-rubber tube (E), the side tube (T) being closed during an experiment by a 
 piece of glass rod. The recording lever (L) writes on a revolving drum. 
 
 Our best results were obtained by using cold instead of a 
 constant current as our blocking agent. 
 
 Fig. 1 is an outline drawing of the apparatus used. 
 
 Fig. 2 shows the arrangement adopted in connection with 
 the nerve. The nerve (N) rests on a metal tube (T) through which 
 water can be kept flowing. E is the situation of the electrodes. 
 If the nerve is excited, the spleen contracts and the recording 
 lever (in fig. 1) falls. If now water at 2 to 3 C. is kept flowing 
 through T, the nerve-impulses are blocked by the cold, and can- 
 not reach the spleen. Immediately the cold water is replaced 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 31 
 
 by warm water at 30 G., the nerv r e again becomes passable by 
 nerve-impulses, and the spleen contracts once more. 
 
 If now the water in T is kept at the low temperature men- 
 tioned, and the nerve is being excited with strong induction 
 shocks all the time, the spleen remains irresponsive ; the nerve- 
 impulses are able to reach T but not to pass it. If then warm 
 water is passed through T, and the block produced by the cold 
 is thus removed, and the spleen continues to be irresponsive, we 
 have a proof that the piece of nerve between E and T has been 
 fatigued. But our experiments have shown us that non-medul- 
 lated nerve is just as difficult to fatigue as medullated nerve. 
 Even after six hours' continuous excitation the nerve is just 
 as excitable as it was at the start, and a full splenic contraction 
 is obtained when the cold block is removed. 
 
 FIG. 2. Arrangement of apparatus in connection with the splenic nerve, 
 s is the spleen, and N the main bundle of nerves. The nerve rests on the 
 metal tube (T) through which water at the required temperature is kept 
 flowing, and on the electrodes (E) which come from the secondary coil of an 
 inductorium. 
 
 We have made similar experiments with vaso-motor nerves, 
 such as the cervical sympathetic nerve in the rabbit, and the 
 sciatic nerve in a curarised dog, and have obtained corres- 
 ponding results. This confirms the work previously published 
 by Eve. 13 Eve excited the cervical sympathetic for twelve 
 hours, and found no loss of excitability at the end of that 
 time. Eve stimulated the nerve below the upper cervical 
 ganglion, and the main object of his work was to ascertain 
 whether any histological evidence of fatigue could be found in 
 the cells of the ganglion. The only change he could find there 
 
 13 Journ. of Physiology, xx., p. 334. 
 
32 THE CROONIAN LECTUBES ON THE 
 
 was a somewhat diffuse staining of the cells by methylene blue, 
 which he attributes to the formation of acid substances in the 
 cells. A blue stain of similar appearance may be induced in the 
 motor cells of the spinal cord, after exhaustion is produced in 
 them by giving strychnine. In such experiments the spinal cord 
 becomes as a rule distinctly acid to litmus paper. Max Verworn 14 
 has more recently employed strychnine as a means of producing 
 fatigue. He considers that the only specific effect of this alkaloid 
 is increase of reflex activity, and he attributes the subsequent 
 paralysis to vascular conditions and the accumulation of fatigue 
 products, among which he places carbon dioxide in the first 
 rank. Eve, on the contrary, did not find that carbonic acid alone 
 produces the effects. 
 
 We must conclude from such experiments that Dr. Waller's 
 theory is unproved, and that while fatigue is demonstrable in 
 nerve-cells, it has never yet been shown to occur in nerve-fibres 
 of either the medullated or hon-medullated variety. 15 
 
 MICRO-CHEMICAL METHODS. 
 
 I must now make an excursion into the histological side of 
 the subject, but this is really a branch of chemistry also, for all 
 the staining properties of tissues are micro-chemical reactions. 
 Of the numerous methods recently invented for the study of the 
 structure of nerve-cells, two stand out as pre-eminently useful. 
 One of these is Golgi's silver-chrome method, and the other is 
 Nissl's methylene blue process. 
 
 Golgi's method and its numerous modifications result in a 
 black staining of the nerve-cells and their branches. The neuron 
 theory, about which you heard so much from Dr. Mott 16 last year, 
 rests mainly on preparations made by this method. The method, 
 valuable as it is, is not, however, capable of demonstrating 
 changes of a pathological kind in the cells. Cells which show 
 even profound changes by other methods, may look quite normal 
 when the silver-chrome process is employed. 
 
 "Arch.fiir (Anat. u.) Physiol, 1900, p. 152. 
 
 15 A possible explanation of the effects described by Miss Sowton is given 
 in a paper which Dr. Brodie and I are sending to the Journal of Physiology, 
 in which the whole question is discussed more fully. 
 
 is The Degeneration of the Neurone," Croonian Lectures, by Dr. Motfc, 
 1900. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 33 
 
 Nissl's method is far more delicate and is extremely simple. 
 Let me very briefly describe it, and the principal results which 
 have accrued from its use. 
 
 THE SIGNIFICANCE OF NISSL'S GRANULE s. 
 
 If portions of the brain or spinal cord are fixed in absolute 
 alcohol, and sections obtained from the hardened pieces are 
 stained by means of methylene blue, the nerve-cells exhibit a 
 characteristic appearance. The nucleus and nucleolus take up 
 the blue stain, and throughout the cell body a number of angular- 
 shaped masses, which are termed Nissl's granules, are also stained 
 blue. These extend some distance into the dendrons, but not 
 into the axon. The substance of which they are composed is 
 termed chromatoplasm, or chromophilic material. The existence 
 of granules in cells which have an affinity for basic dyes like 
 methylene blue is not at all common ; the granules in the 
 majority of the white blood corpuscles, for instance, have an 
 affinity for acid dyes. Micro-chemical methods have shown that 
 the main constituent of the Nissl granules is nucleo proteid. 
 The name kineto-plasm has been given to it by Marinesco in 
 order to express the idea that it forms a source of energy to the 
 cell. It can hardly be denied that the substance of which the 
 granules are composed, forming as it does so large a proportion 
 of the cell contents, and made of a material in which nuclein 
 forms an important constituent, is intimately related to the 
 nutritional condition of the neuron. Some have even compared 
 it to the granular material which is present in secreting cells ; 
 in these cells before secretion occurs the granules accumulate, 
 and during the act of secretion they are discharged and converted 
 into constituents of the secretion. It is stated by some observers 
 that the Nissl granules are used up during the discharge of 
 energy from nerve-cells, and that this may be regarded as a 
 visible sign of fatigue ; it certainly is the case that if the cells 
 are examined after an epileptic fit, in which there has been a 
 very massive discharge of impulses, the Nissl granules have 
 disappeared, or at least broken up into fine dust-like particles, 
 so that the cell presents a more uniform blue staining. It is, 
 however, doubtful whether this is due to a transformation 
 associated with intense activity, or whether it may not be caused 
 3 
 
34 THE CBOONIAN LECTURES ON THE 
 
 by venosity of the blood. The cells are very sensitive to altered 
 vascular conditions ; anaemia, for instance, produces a similar 
 change accompanied with swelling of the cell, and swelling and, 
 in extreme cases, extrusion of the nucleus. 
 
 Since attention has been directed towards the Nissl granules, 
 a literature which has become alarmingly vast during the last few 
 years has sprung up in relation to them. This is quite easy to 
 understand, for neurologists have by this sensitive test been able 
 to identify changes in the cells which could not be detected by 
 the previous methods of staining. Thus the cells have been 
 examined in various diseases, and after being subjected to the 
 action of various poisons. In a new subject of this kind there is, 
 as would be expected, considerable divergence of views, and even 
 the fundamental question has not yet been answered satisfactorily 
 whether the Nissl granules are present as such in the living cell, 
 or whether they are artifacts produced by the fixative action of 
 strong alcohol. The fact that they cannot be demonstrated when 
 the cells are stained by the injection of methylene blue into the 
 circulation before the animal is killed is a very strong piece of 
 evidence in favour of the latter view ; though it may be urged 
 against this, that methylene blue used in this way is a poison 
 and so not calculated to give us normal results. But, whichever 
 view is correct, the method is a valuable one, and Nissl's views 
 on this question appear to be indisputable ; they are briefly as 
 follows : Healthy cells fixed and stained in a constant manner 
 will appear the same under constant optical conditions, and the 
 appearances then seen form the equivalent of such healthy cells 
 during life. It follows that if cells prepared by the same method 
 and examined under the same conditions show a difference 
 from the equivalent or symbol of healthy cells, the difference is 
 the measure of some change that has occurred during life. 
 
 Chromatolysis is the term applied to designate t the disappear- 
 ance or disintegration of the Nissl granules. The process gener- 
 ally begins at the periphery of the cell and in the dendrons, but 
 in advanced cases the whole cell may be affected. We have 
 already alluded to the fact that chromatolysis occurs in various 
 abnormal states, and the diminution of the chromophilic nucleo- 
 proteid indicates a diminution of the vital interaction of the 
 highly phosphorised nucleus with the surrounding cell proto- 
 plasm. Chromatolysis alone is not indicative of cell destruction, 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 35 
 
 and a cell may recover its function afterwards. The integrity of 
 the nucleus and of the fibrils appears to be much more important 
 to the actual vitality of the cell. 
 
 When a nerve-fibre is cut across the distal segment undergoes 
 Wallerian degeneration ; this is an acute change. But the nerve- 
 cell and the piece of the nerve-fibre still attached to it do not 
 remain unaffected. If regeneration of the fibre and restoration 
 of function take place no change is observable. But before 
 regeneration occurs (and in the central nervous system regenera- 
 tion never occurs) the cell and its processes undergo a slow 
 chronic wasting ; one of the earliest signs of this disiise atrophy 
 is chromatolysis. Warrington 17 has recently shown another 
 interesting fact, namely, that section of the posterior roots of the 
 spinal nerves causes chromatolysis in the anterior nerve-cells of 
 the same side ; this indicates that loss of sensory stimuli pro- 
 duces a depression of the activity and metabolic functions of the 
 spinal motor cells. This accords quite well with the physiological 
 effects observed under these conditions. The drawings in the 
 accompanying plate (Plate I.) show the normal appearance of a 
 nerve-cell when stained by methylene blue (A). B is a cell 
 which shows chromatolysis as the result of status epilepticus, 
 and C shows much the same condition as a result of cerebral 
 anaemia. D illustrates the effect of prolonged narcosis, to be 
 referred to later in this lecture (see p. 40). 
 
 SLEEP AND NARCOSIS. 
 
 We have now considered the question of fatigue in many of 
 its aspects. Let us next turn our attention to a brief considera- 
 tion of sleep, Nature's great restorer for exhausted "nerves." 
 Theories to account for sleep have been numerous, and some of 
 these are chemical. Thus certain observers have considered that 
 sleep is the result of the action of chemical materials produced 
 during waking hours, which have a soporific effect on the brain ; 
 according to this theory awakening from sleep is due to the 
 action of certain other materials produced during rest, which 
 have the opposite effect. Obersteiner has gone so far as to 
 consider that the soporific substances are reducing in nature, and 
 
 17 Journ. of Physiology, xxv., p. 462, 1900. 
 
PLATE I. NISSL'S GRANULES. 
 
 A. Normal pyramidal cell of human cerebral cortex. 
 
 B. Swollen cedematous pyramidal cell from a case of status epilepticus. 
 
 Notice diffuse staining and absence of Nissl's granules ; the nucleus is 
 enlarged and eccentric. The lymph space around the cell is enlarged. 
 
 C. Pyramidal cell of dog after ligature of vessels going to the brain and 
 consequent anaemia. Notice the great swelling of the nucleus and 
 advanced chromatolysis, most marked at the periphery of the cell. 
 Figs. A, B, and C are after Mott ; magnification in each case 700 
 diameters. 
 
 D. Skeleton condition of cerebral cell in a rabbit produced by six hours' 
 anaesthesia with ether. After HAMILTON WEIGHT. 
 
PLATE I. 
 
 i53N*,**r--.. ' J 
 
 Bale & Danidsson, Ltd., London. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 37 
 
 others regard them as alkaloidal (leucomaines). These theories 
 all rest on the flimsiest foundations, and none has yet been found 
 to stand experimental tests. 
 
 The nerve-cell, like so many other cells of our bodies, exhibits 
 a rhythmical tendency. In the heart the alternate periods of 
 rest and action are both short ; in many other involuntary 
 muscles, such as those of the spleen and intestine, the periods 
 are longer. If we place nerve-cells in the same category, the 
 periods are variable in length, but as a rule are longer still. 
 Some years ago Dr. Sydney Einger showed that certain mixtures 
 of inorganic salts are capable of maintaining the rhythmic activity 
 of cardiac muscle, cilia and similar structures. Quite recently 
 these experiments have been repeated and confirmed in two 
 American laboratories, one under Professor Howell at Baltimore, 
 the other under Professor Loeb at Chicago. Although all the 
 essential facts of Dr. Ringer's work have been shown to be 
 correct, they are now in the light of the modern theory of 
 solutions interpreted differently. Loeb, in particular, has shown 
 that ionic action is at the root of the matter. There are differ- 
 ences noted in different forms of contractile tissue, but in all 
 there must be a nicely balanced admixture of the ions in order 
 that rhythmic action may be maintained. Some ions (like OH) 
 have little or no effect ; others (like Na) stimulate ; and others 
 (like Ca) inhibit action. An optinum saline solution is one in 
 which the stimulating ions are mixed in due proportion with 
 those which restrain activity. The inorganic constituents of the 
 body would perhaps have been the lasty one would have antici- 
 pated to act in this way, but there are many unlikely things that 
 happen during life. If we in the future find that nerve-cells are 
 to be considered on all fours with contractile cells, it is possible 
 that it will be found that the phenomenon of alternate periods 
 of action and rest can be explained by the comparatively simple 
 action of inorganic substances or of their constituent ions. 
 
 This, however, is after all not much more than a wild guess 18 
 and we must return to the safer regions of experiment. The 
 introduction of the Golgi method opened a fresh field for investi- 
 
 18 That such a view is not entirely outside the bounds of probability is 
 shown by the fact that certain electrolytes, notably bromides of the halogens, 
 possess the power of modifying the normal rhythm of the brain-cells. 
 
38 THE CROONIAN LECTURES ON THE 
 
 gators, and several have sought to find by that method a con- 
 dition of the neurons produced by narcotics, which is different 
 from that which obtains in the waking state. 
 
 Demoor and several others found that in animals in which 
 deep aneesthesia has occurred that the dendrites exhibit what he 
 calls moniliform swellings, that is, a series of minute thickenings 
 or varicosities. On the strength of this observation, he has 
 formulated what we may call a bio-physical theory of sleep. 
 In the waking state, the neighbouring nerve-units are in contact 
 with each other ; transmission of nerve-impulses from neuron to 
 neuron is then possible, and the result is consciousness ; during 
 sleep the dendrites are retracted in an amoeboid manner ; the 
 neurons are therefore separated, and the result is unconsciousness. 
 
 Lugaro, on the other hand, takes the precisely contrary view. 
 He was not able to discover moniliform enlargements and his 
 bio-physical hypothesis is that the interlacing of dendrites is 
 much more intimate during sleep than during consciousness. 
 He therefore explains sleep by supposing that the definite and 
 limited relationships between neurons no longer exist, but are 
 lost and rendered ineffective by the universality of the connecting 
 paths. It is not very difficult to explain such divergence of 
 views, for they both depend mainly on observations made by a 
 single method ; and the method itself is open to objection. It is 
 one which gives even in the same brain most inconstant results, 
 and is not calculated to show much more than a mere outline of 
 a few of the cells and their branches. So much doubt has arisen 
 of late in regard to the trustworthiness of the method, that many 
 neurologists are beginning to doubt whether the neuron theory 
 implying absolute non-continuity of nerve-units has been satis- 
 factorily proved, and there is a tendency to return to the idea 
 of a connecting network not very different from that originally 
 put forward by Gerlach. 
 
 A more satisfactory investigation of the effect of ansestheti-cs 
 on nerve-cells has been carried out by Dr. Hamilton Wright, 
 Director of the Pathological Institute of the Federated Malay 
 States. He began this work some years ago, and carried out the 
 majority of his experiments in my laboratory, and since his 
 arrival in the Straits Settlements has completed them, and pub- 
 lished his results in two papers in the Journal of Physiology. 
 
 19 Vol. xxvi., p. 30, 1900 ; vol. xxvi., p. 362, 1901. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 
 
 39 
 
 He used rabbits and dogs, and subjected them to ether and 
 chloroform narcosis for periods varying from half an hour to nine 
 hours. In both animals he found that the nerve-cells are 
 affected, but in rabbits much more readily. This accords quite 
 well with what is known regarding the susceptibility of rabbits as 
 compared to dogs towards the influence of these narcotising 
 agents. In a rabbit the nerve-cells, especially of the cerebrum, 
 show changes even after only half an hour's anaesthesia, but in 
 dogs at least four hours' anaesthesia must be employed. By the 
 
 A B 
 
 FIG. 3. Moniliform enlargements on dendrites of nerve-cells, rendered 
 evident by Cox's method. A, in a cortical cell of a rabbit ; B, in a correspond- 
 ing cell of a dog's brain, after six hours' aneesthetisation with ether in each 
 case. HAMILTON WRIGHT. 
 
 Golgi method (Cox's modification) the moniliform enlargements 
 can be seen. These become more numerous, larger, and encroach 
 more and more on the dendritic stems, the longer the anaesthesia 
 is kept up. The accompanying illustrations show the appearances 
 seen. 
 
 Lugaro's failure to find these appearances is doubtless due to 
 his not having maintained the anaesthesia long enough in his 
 dogs. 
 
 Wright started his work with a bias in favour of Demoor's 
 bio-physical theory, but he soon found that the theory was 
 
40 THE CKOONIAN LECTURES ON THE 
 
 untenable ; the results of his observations have shown him that 
 the action of anaesthetics is bio-chemical rather than bio-physical, 
 and he has been led to this conclusion by the employment of 
 other histological methods, particularly the most sensitive one we 
 possess, namely, the methylene-blue reaction. 
 
 Owing to the chemical action of the anaesthetic in the cells, 
 the Nissl bodies have no longer an affinity for methylene-blue, 
 and the cells consequently present what Wright calls a rarefied 
 appearance ; when this becomes marked the cells appear like the 
 skeletons of healthy cells (see Plate I, D). In extreme cases the 
 cells look as though they had undergone a degenerative change, 
 and after eight or nine hours' anaesthesia in dogs, even the nucleus 
 and nucleolus lose their affinity for basic dyes. The change, how- 
 ever, is not a real degeneration and passes off when the drug 
 disappears from the circulation. Even after nine hours' anaes- 
 thesia the cells return to their normal condition within forty-eight 
 hours, the cells stain normally, moniliform enlargements have 
 practically disappeared, and no nerve-fibres show a trace of 
 Wallerian degeneration. The pseudo-degenerative change pro- 
 duced by the chemical action of the anaesthetic no doubt inter- 
 feres with the normal metabolic activity of the cell-body, and this 
 produces effects on the cell-branches. In the early stages of 
 Wallerian degeneration, the branch of the nerve-cell which we 
 call the axis-cylinder, presents swellings or varicosities, produced 
 by hydration or some similar chemical change. The moniliform 
 enlargements seen during the temporary pseudo-degenerative 
 effects produced by anaesthetics are comparable to this. 20 These 
 enlargements are therefore not the primary cause of loss of 
 consciousness, but are merely secondary results of changes in the 
 cell-body. When a tree begins to wither the earliest apparent 
 change is noticed in the -branches most remote from the centre of 
 nutrition, the root ; as the changes in the centre of nutrition 
 become more profound the larger branches become implicated, 
 but the seat of the mischief is not primarily in the branches. 
 This illustration may serve to render intelligible what is found in 
 nerve-cells and their branches. 
 
 20 Some observers look upon the varicosities as artifacts. If they are they 
 ought to have been found in all Wright's specimens, for the method of 
 preparation was the same throughout. 
 
CHEMICAL SIDE OP NERVOUS ACTIVITY 41 
 
 Whether the appearances found in dogs and rabbits are appli- 
 cable to the human subject is another question. I am inclined 
 to think that we may safely regard them as such ; there is no 
 reason why an anaesthetic should act differently in different 
 animals. The resistance of the animal is a variable factor, and 
 this causes a variation in degree only ; the effect is probably the 
 same in kind for all animals, man included. 
 
 But I feel with Dr. Wright that we should be very chary in 
 concluding that the artificial sleep of a deeply-narcotised animal 
 is any criterion of what occurs during normal sleep. The sleep 
 of anaesthesia is a pathological condition due to the action of a 
 poison. The drug reduces the chemico-vital activities of the 
 cells, and is, in a sense, dependent on an increasing condition of 
 exhaustion, which may culminate in death. Normal sleep, on the 
 other hand, is not produced by a poison, or at any rate we have 
 no evidence of any poison ; it is the normal manifestation of one 
 stage in the rhythmical activity of nerve-cells, and though it may 
 be preceded by fatigue or exhaustion, it is accompanied by repair, 
 the constructive side of metabolic activity. 
 
42 THE CROONIAN LECTURES ON THE 
 
 LECTUBE III. 
 PATHOLOGICAL SIDE OP THE SUBJECT. 
 
 MY first and second lectures have been concerned with physio- 
 logical considerations. I propose in this and the next lecture to 
 turn to more strictly pathological questions. I have already 
 stated my belief that the comparatively new subject of chemical 
 pathology has a great future before it, and this is as true for 
 nervous diseases as for diseases of other parts of the body. Up 
 to the present time, comparatively few pathologists have worked 
 at the chemical side of nervous disease, and a few years ago, 
 when Dr. Mott and I started our work, this branch of investi- 
 gation was practically untouched. 
 
 The researches which we may consider to be in an approxi- 
 mately complete condition are three in number. They are : 
 
 (1) The bearing of chemical research on hyperpyrexia. 
 
 (2) The chemical pathology of General Paralysis of the Insane. 
 
 (3) The chemistry of Wallerian degeneration. 
 
 I propose to consider the first two of these to-day, and to 
 reserve the third for my final lecture. 
 
 In my account of these investigations I shall find it necessary 
 to repeat to some extent what Dr. Mott stated in his Croonian 
 Lectures last year. It is almost impossible to avoid this, if the 
 presentation of the subject is to be complete. I shall endeavour, 
 however, to make this part of what I have to say as short as 
 possible, and dwell more fully on our work of the year that has 
 intervened since Dr. Mott addressed the College. 
 
 THE COAGULATION TEMPERATURE OF CELL-GLOBULIN AND ITS 
 BEARING ON HYPERPYREXIA. 
 
 When in 1893 I published some work on the proteids of 
 nervous tissues, 1 I little thought that the subject would turn 
 
 1 Journ. of Physiology, 1893, xv., p. 90. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 43 
 
 out to be one of practical pathological interest. The history of 
 physiology is full of such surprises. Physiologists qua physio- 
 logists work rather from the academic than from the practical 
 standpoint ; but as time passes nearly every piece of work which 
 they do is discovered by pathologists to have practical bearings. 
 The first workers at the obscure subject of the chemistry of cell- 
 nuclei little thought they were paving the way for the proper 
 understanding of the uric acid problem. The earlier workers at 
 the physiology of the thyroid gland did not foresee the applica- 
 tion of their work to the correct knowledge of cretinism and 
 myxoedema, and to the cure of these conditions. Many other 
 instances might be given, but my hearers will themselves be able 
 to supply them. 
 
 It is well known that there are various factors that influence 
 the temperature of heat-coagulation of proteid substances. 
 Among these the rate of the rise of temperature is one of some 
 importance. This was clearly shown in the work of Corin and 
 Ansiaux 2 on serum, and in that of Hewlett 3 on white of egg. 
 These observers found that if the temperature is maintained long 
 enough below the point at which heat-coagulation is usually 
 stated to occur, not merely opalescence, but the formation of 
 flocculi will take place. 
 
 In performing the process of fractional heat-coagulation with 
 saline extracts of various organs and tissues, I 4 have shown that 
 in nearly all of them a proteid is present which coagulates at 
 an extremely low temperature (45 to 50 C.). This proteid is a 
 globulin, and it appears to be as characteristic of protoplasmic 
 structure as nucleo-proteid. Whether this proteid is the same 
 in extracts of all tissues is uncertain, but the term cell-globulin 
 may be provisionally employed to designate it. 
 
 The next question which arises is whether the behaviour of 
 saline extracts of cellular tissues is a trustworthy guide to teach 
 us the condition of the proteids as they actually exist in proto- 
 plasm. As a help in answering this question, I must allude to 
 
 - Bulletin de VAcad. roy de Belgique, xxi., p. 3, 1891. 
 
 3 Journ. of Physiology, xiii. , p. 494, 1893. 
 
 4 The papers relating to this subject are numerous, and were all published 
 in the Journal of Physiology. A summary of them will be found in my 
 article on the Chemistry of the Tissues and Organs in Schafer's '* Text- 
 book of Physiology," vol. i. 
 
44 THE CKOONIAN LECTURES ON THE 
 
 the work of Brodie and Eichardson, 5 and Vernon. G These in- 
 vestigators show in the case of muscle that the shortening which 
 occurs during heat-rigor takes place in a series of steps ; the 
 temperatures at which these steps occur are the same as those 
 at which the individual proteids separate out during the frac- 
 tional heat-coagulation of an extract of muscular tissue. Thus 
 in mammalian muscle, the two principal shortenings occur at 
 47 and 56 0., the coagulation temperatures of the two principal 
 muscular proteids. In frog's muscle there are three steps, at 
 40, 47 and 56 C. respectively, which correspond to the three 
 proteids that can be separated out in a saline extract of this 
 variety of muscular tissue. 
 
 Brodie also showed another important point, namely, that 
 after the first step has occurred in the shortening, the muscles 
 lose their irritability. In other words, in order to destroy the 
 vitality of muscular tissue, it is not necessary to raise the tem- 
 perature sufficiently high to coagulate all its proteids, but that 
 when one of the muscular proteids has been coagulated the 
 living substance as such is destroyed; the proteids of muscle 
 cannot be regarded as independent units ; the unit is proto- 
 plasm, and if one of its essential constituents is destroyed, proto- 
 plasm as such ceases to exist. 
 
 I think we may safely infer that what is true for muscle is in 
 the main true for other tissues, and that the results which have 
 been obtained by the examination of saline extracts of these 
 tissues can be safely applied to the elucidation of the compo- 
 sition of the protoplasm of which they are composed. 
 
 We can now pass to the application of these general principles 
 to nervous tissues, especially in connection with the question 
 of hyperpyrexia. Mott's histological observations have proved 
 that in cases of death from hyperpyrexia the nerve-cells show a 
 disappearance of the Nissl granules; both cell - bodies and 
 dendrons show a diffuse blue staining with methylene blue. He 
 has proved that this is not due to the toxin of the disease, but 
 to the high temperature. It is a familiar fact that very high 
 body temperature is incompatible with life. Marinesco 7 has 
 
 5 Phil. Trans., cxci., B. 127, 1899. 
 " Journ. of Physiology, xxiv., p. 239, 1899. 
 
 7 Recherches sur les lesions des centres tierveux consecutive a Vhyper- 
 tliermie Expert-mentals et a la Fievre, Revue Neurologique, 1899. See also 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 45 
 
 pointed out in experiments on hyperthermia in animals that a 
 temperature of 47 C. is immediately fatal; a temperature of 
 45 C. kills in an hour or two ; a temperature of 43 C. kills 
 after a longer lapse of time. Moreover, the occurrence of 
 death is coincident with the break-down of the nerve-cells in the 
 manner just indicated. It is possible that analogous changes 
 occur in other parts of the body also, but these do not seem 
 to have been specially investigated. The nerve-cells are un- 
 doubtedly essential to healthy life, and lend themselves very 
 readily to microscopic investigation by the methylene - blue 
 process, A temperature of 47 C. leads to a practically instan- 
 taneous disappearance of the chromatophile granules ; the same 
 change occurs at 45 C. in a few hours ; at 43 C. a longer lapse 
 of time is necessary. 
 
 The coincidence of the fatal temperature (47 C.) with that 
 of the coagulation temperature of cell-globulin is very striking, 
 and we argue that, as in muscle, the coagulation of even the 
 lowest coagulating proteid of nerve-cells must produce a destruc- 
 tion of the life of their protoplasm, and so a distinct chemico- 
 physical cause can be found for death due to hyperpyrexia. 
 Still a temperature as high at 47 C. (117 F.) in man is un- 
 known, and we thought it possible that the proteid in question 
 would coagulate at a lower temperature, if it was kept at that 
 temperature a sufficient length of time. We proceeded to put 
 the suggestion to the test of experiment, fully anticipating, in 
 the light of the work of Hewlett and others alluded to before, 
 that the supposition would turn out to be correct. 
 
 We made saline extracts of the grey matter of the brains of 
 cats and human beings, and found that the first crop of flocculi 
 separates out at 47 C. when the rate of heating is rapid. But if 
 the temperature of the water bath is maintained at 44 C. for 
 two hours, precipitation of the proteid occurs at this temperature. 
 At 42 C. (108 F.), three to four hours' heating brought down 
 the coagulum at that temperature. At 40 to 41 there was no 
 coagulation even after eight hours' heating. 
 
 We proved the same point in another way. A cat was after 
 anaesthetisation rapidly killed by bleeding to death ; the brain was 
 
 Goldscheider and Flatau, Normale und Pathol. Anat. der Nervenzcllen, 
 Berlin, 1898. 
 
46 THE CEOONIAN LECTURES ON THE 
 
 removed and divided into two equal halves. A saline extract of 
 one half was made immediately ; the other half was heated to 
 47 G. for an hour and then similarly treated. The extract of 
 the first (the normal) half contained 0*674 per cent, of proteid, 
 and fractional heat coagulation revealed the presence of proteids 
 which came down at 47, 56 to 65, and 72 C. respectively 
 (see p. 9). In the extract of the second (the heated) half 
 the total percentage of proteid was only 0-144 ; the 47 C. 
 coagulum was absent, but the other two were obtained. 
 
 In the next experiment the half-brain was heated to 42 
 instead of 47 C. It was kept at 42 C. for five hours. The 
 extract of the normal half-brain contained 0*483 per cent, of 
 proteid and gave the usual three crops of coagula ; the extract 
 of the half-brain which had been heated to 42 C. contained only 
 4 226 per cent, of proteid, and the coagulum at 47 C. was 
 absent. 
 
 The chemical examination of brain tissue as fresh as pos- 
 sible thus gave results which exactly correspond to those 
 obtained in the experiments with saline extracts. 
 
 We have not repeated Marinesco's experiments on hyper- 
 thermia in animals, but for histological purposes we have per- 
 formed the experiment of exposing the brain in situ immediately 
 after death to an elevated temperature. In the case of one cat 
 the brain was kept at 44 to 45 C. for one and a half hours, and 
 in another at 42 to 43 C. for three and a half hours. In 
 each case, and particularly in the first, the cells exhibited 
 chromatolysis. 8 
 
 We may therefore sum up by saying that our experiments 
 fully confirm our hypothesis that the physico-chemical cause 
 of death from hyperpyrexia is the coagulation of cell-globulin. 
 When this constituent of cell-protoplasm is coagulated, the 
 protoplasm as such is destroyed. The temperatures at which 
 such coagulation is most readily produced is 47 C. But tem- 
 peratures as low as 42 C. will have the same effect, provided 
 the heating is continued long enough. These chemical changes 
 in the brain substance are demonstrable by experiments with 
 
 s Full details of all these experiments and observations will be shortly 
 published in a paper by Dr. Mott and myself in the forthcoming volume 
 (vol. ii.) of Mott's Archives of Neurology. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 47 
 
 saline extracts of that tissue, or with the "surviving" brain 
 of animals just killed. They are coincident with the histo- 
 logical (chromatolytic) changes in nerve-cells, which can be ren- 
 dered evident by the use of the methylene-blue method. The 
 expression coagulation necrosis employed by Marinesco for this 
 appearance is therefore justifiable. Marinesco and others who 
 have employed exclusively histological methods of research, 
 have naturally failed to grasp the chemical meaning of their 
 
 FIG. 4. Section of spinal cord from a case of hyperpyrexia, the tempera- 
 ture being 109 F. before death. The whole of the cells throughout the 
 central nervous system showed a diffuse homogeneous staining with methy- 
 lene blue. The Nissl granules had entirely disappeared from the processes 
 and body of the cells, and the stainable substance had a fine, dust-like 
 appearance. Magnification 400 diameters. MOTT. 
 
 observations, and have consequently missed the connection of 
 the temperature necessary to produce these changes with that 
 of the coagulation temperature of cell-globulin. Lastly, though 
 the nerve -cells are those which have been more specially in- 
 vestigated by these methods, it is by no means improbable 
 (looking at the wide distribution of cell-globulin) that many 
 other cells of the body are affected by high temperatures in 
 
48 THE CROONIAN LECTURES ON THE 
 
 a corresponding manner ; some varieties of what is called 
 "cloudy swelling" are without doubt instances of coagulation 
 necrosis. The accompanying figure (fig. 4) illustrates the histo- 
 logical changes in nerve-cells referred to. 
 
 CHEMICAL PATHOLOGY OF GENERAL PARALYSIS OF THE INSANE. 
 
 General Paralysis of the Insane is a para-syphilitic affection 
 like tabes, with which it is, pathologically speaking, identical. It 
 is a premature, primary, progressive decay of the neuron, affect- 
 ing especially those structures which have been developed latest. 
 To the naked eye the extensive degenerative and wasting pro- 
 cess which occurs, especially in the frontal and central convolu- 
 tions, is perfectly evident. Microscopical examination of the 
 diseased brains reveals degenerative changes in the cells ; and 
 the perivascular lymphatics are seen (by Marchi's method of 
 staining) in acute cases to contain phagocytes filled with black- 
 stained fatty matter. During the course of the disease there are 
 frequently seizures of an epileptiform or apoplectiform kind, and 
 after recovery of the patient from each of these fits he is, as a 
 rule, worse mentally. Each fit apparently indicates the break- 
 down of a new focus of cerebral matter. 
 
 The place of the atrophied brain substance within the cranium 
 is taken by excess of cerebrospinal fluid. It is often possible to 
 obtain as much as one or two hundred cubic centimetres of this 
 fluid. 
 
 The main object of our research was to examine the cerebro- 
 spinal fluid, and to attempt to discover in it some substance or 
 substances derived from the disintegration of the brain-matter, 
 which passing thence into the general circulation would produce 
 auto-intoxication, and thus account for some of the symptoms of 
 the disease. How far this object has been attained, will be 
 discussed at the conclusion of this lecture. 
 
 Our methods and results have already been published in full 
 in the Philosophical Transactions of the Eoyal Society? and all 
 I shall attempt here is to describe these in more general terms, 
 in order to pave the way for the consideration of the subject of 
 nervous degeneration in my final lecture. 
 
 Mott and Halliburton, "The Physiological Action of Choline and 
 Neurine," Phil. Trans., Series B, vol. cxci., pp. 211-267, 1899. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 
 
 Normal cerebrospinal fluid is alkaline to litmus and contains 
 a very small percentage of solids (see first lecture). The fluid 
 from cases of General Paralysis is not only more abundant, but 
 is also richer in solids ; this is principally due to excess of proteid 
 material. The average percentage of proteid in eight specimens 
 was 0-24, that is about three times as much as is found in 
 cerebrospinal fluid in cases of spina bifida. It is alkaline like 
 the normal fluid. Fibrinogen is absent as in the normal fluid ; 
 
 FIG. 5. Crystals of the platino-chloride of choline prepared from a 
 solution of choline hydrochloride. Crystallised from 15 per cent, alcohol. 
 
 proteoses and peptone are also absent. There is a small quantity 
 of albumin present ; in the normal fluid albumin is absent. The 
 most abundant proteid, however, is nucleo-proteid ; in one case 
 sufficient was present to produce intravascular coagulation, when 
 10 cc. of the fluid were injected into the jugular vein of a cat. 
 
 Another marked distinction between the normal and the 
 pathological fluid is the presence in the former of a reducing 
 substance, and the absence of this, as a rule, in the latter ; in 
 only two out of fourteen cases was it found. 
 4 
 
50 
 
 THE CROONIAN LECTURES ON THE 
 
 But the most noteworthy distinction between the two fluids 
 is the presence of abundance of choline in the specimens removed 
 from cases of General Paralysis. This can be identified chemically 
 by numerous tests, of which the most important are the characters 
 (solubility, crystalline form, &c.), of the platino-chloride. The 
 accompanying figures show the shape of these yellow octahedral 
 
 FIG. 6. Crystals of the platino-chloride of the base separated from 
 cerebrospinal fluid in cases of General Paralysis of the Insane. Crystallised 
 from 15 per cent, alcohol. The identity of this base with choline is not only 
 shown by the form of these crystals, but by its solubilities and by other 
 numerous reactions described in full in the paper referred to. 
 
 crystals. The chemical examination of the fluid supports our 
 contention that the cerebrospinal fluid acts as the lymph of the 
 brain, and when the disintegration of the cerebral tissue is in- 
 creased, as in General Paralysis, the fluid contains the products 
 of such disintegration (e.g., choline, nucleo-proteid). The greater 
 number of the specimens of cerebrospinal fluid we have examined 
 were removed from the cadaver as soon as possible after death. 
 We have also had the opportunity of examining four specimens 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 51 
 
 removed during life by lumbar puncture from cases of General 
 Paralysis. 10 The results obtained with these are identical with 
 those obtained from the post-mortem specimens. We have also 
 secured on several occasions blood removed for remedial pur- 
 poses from such patients by venesection, and we regard one of 
 the most important outcomes of our work, the discovery that the 
 blood also contains the same toxic material during a seizure. 
 It is not present in the urine. 
 
 The presence of choline can be shown not only by the 
 chemical reactions just referred to, but also by physiological 
 tests. This necessitated the study of the physiological action of 
 choline, an undertaking of a prolonged nature involving experi- 
 ments on the heart, blood-vessels, respiratory movements, and 
 so forth. To this we added a similar investigation on the 
 physiological action of the closely-related alkaloid neurine. The 
 substance separated out from the cerebrospinal fluid and blood 
 of these patients acts precisely like choline in every particular. 
 The action of neurine is different, and this alkaloid is much more 
 toxic. The absence of neurine from the cerebrospinal fluid was 
 also demonstrated by chemical testing. 
 
 The principal physiological actions of choline or choline 
 hydrochloride, using small doses (1 to 5 cc. of 0-2 per cent, 
 solution) injected intravenously in anaesthetised dogs and cats 
 are the following. We used weak solutions, for we sought as far 
 as possible to note the effects produced by solutions of such 
 strength as would be comparable to the amount of the base 
 presumably present in pathological cerebrospinal fluid. 
 
 (1) Choline produces a temporary fall in arterial blood- 
 pressure. 
 
 (2) This is in some measure due to its action on the heart. 
 
 (3) It is also, and probably mainly, due to dilatation of the 
 peripheral vessels, especially in the intestinal area. 
 
 (4) The kidney and limbs undergo a passive lessening of 
 volume secondary to the fall in general arterial pressure. 
 
 (5) The spleen contracts markedly,- and when this passes off, 
 its normal curves are greatly exaggerated. 
 
 (6) We obtained no evidence of any direct action of the base 
 on the cerebral vessels. 
 
 10 We are indebted for these to Dr. John Turner, Essex County Asylum. 
 
52 
 
 THE CBOONIAN LECTURES ON THE 
 
 FIG. 7. Half the original size. R. is a tracing of the respiratory move- 
 ments taken by the tambour method ; B. P. , a tracing of the blood pressure 
 from the carotid artery; A., abscissa of the blood pressure; T., time in 
 seconds ; S, signal, the alteration of level of which indicates the period during 
 which the material was injected into the jugular vein. The same letters 
 have the same significance in subsequent tracings. The arrow in each case 
 indicates the direction in which the tracing is to read ; this in nearly all 
 cases is from left to right. 
 
 Fig. 7 shows the effect in a dog of injecting 6 cc. of a 0*2 per cent, solution 
 of a choline hydrochloride. There is a fall of arterial pressure but no effect 
 on respiration. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 
 
 53 
 
 FIG. 8. Half the original size. Similar effect in a dog produced by the 
 injection of 10 cc. of cerebrospinal fluid removed from a case of ^General 
 Paralysis of the Insane. 
 
THE CBOONIAN LECTURES ON THE 
 
 FIG. 9. Half the original size. Effect in a dog of saline solution of 
 the alcoholic extract of 70 cc. of blood removed during a seizure from a 
 patient suffering from General Paralysis of the Insane. As in figs. 7 and 8, 
 there is no effect on respiration (R. ), but there is a well-marked temporary 
 fall of arterial blood pressure (B.P.). In the same blood, choline was identi- 
 fied chemically. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 
 
 55 
 
 (7) The action on the splanchnic vessels is due to the direct 
 action of the drug on the neuro- muscular apparatus of those 
 vessels, for after the influence of the central nervous solution has 
 
 ' i i I 
 
 . i .1 I I u.l L* ' I * I 
 
 i , i i I 
 
 FIG. 10. Original size. Effect of injecting 5 cc. of a solution of choline 
 hydrochloride (0-2 per cent.). The fall of blood pressure is accompanied by 
 a dilatation of the intestinal vessels ; this is shown by the rise of the lever 
 of the Marey's tambour connected with the intestinal plethysmograph (I.O.). 
 Dog. 
 
 been removed by section of the spinal cord, or of the splanchnic 
 nerves, choline still causes the typical fall of arterial pressure. 
 The action of peripheral ganglia may be excluded by previously 
 poisoning the animal with nicotine. 
 
56 
 
 THE CBOONIAN LECTUKES ON THE 
 
 (8) There is little or no effect on the respiration. 
 
 (9) Section of the vagi makes no difference in these experi- 
 mental results. 
 
 FIG. 11. Original size. Tracing of intestinal oncometer (T.O.) and 
 arterial blood pressure (B.P. ) in a cat ; 10 cc. of cerebrospinal fluid from 
 a case of General Paralysis were injected ; the same effect was obtained in 
 the same animal by injecting 2 cc. of a O2 per cent solution of choline. The 
 fall of blood pressure is at first mainly cardiac in origin, for the oncometer 
 tracing first follows the fall of arterial blood pressure passively ; it, however, 
 soon rises, indicating dilatation of the peripheral vessels. 
 
 (10) Previous atropinisation of the animal causes a great 
 difference ; it abolishes the fall of arterial pressure, though there 
 is still some dilatation of splanchnic blood-vessels. In fact, very 
 often injection of choline after atropine produces a rise instead of 
 a fall of blood pressure. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 57 
 
 I need not detain you by entering into details concerning the 
 action of neurine. Suffice it to say that it is much more 
 poisonous, affects the heart more, causes peripheral constriction 
 rather than dilatation of blood-vessels, stimulates and then 
 paralyses the respiratory movements, and has a curare-like action 
 on voluntary muscles. 
 
 Illustrations of the numerous tracings we have taken in 
 working out these facts are given in the paper already referred 
 to. I reproduce here a few of the most typical. (These at the 
 actual lecture were shown as lantern slides.) 
 
 I. ... li ... I I i .. I .... 1 .... I i- 
 
 FIG. 12. FIG. 13. 
 
 FIG. 12. Effect on injecting extract of cat's brain before atropine. 
 
 FIG. 13. Effect after atropine of the same extract in the same animal 
 (cat) ; the fall of blood pressure seen in fig. 12 is here replaced by a slight rise. 
 With pure solutions of choline the rise is generally more marked. 
 
 Both these figures are considerably reduced in size ; the amount of reduc- 
 tion can be judged from the measure of the height of blood pressure indicated 
 in millimetres on the side of fig. 12. 
 
 Fig. 7 shows the effect of 5 cc. of a - 2 per cent, solution of 
 choline hydrochloride in physiological saline solution. The 
 effect (fall of blood pressure, no effect on respiration) is just the 
 same as that produced by the substance separated out from 
 cerebrospinal fluid from cases of General Paralysis (tig. 8). 
 
 The next figure (fig. 9) shows the result of injecting into a dog 
 the saline solution of the alcoholic extract of 70 cc. of blood 
 removed during a seizure from a patient suffering from the same 
 disease. Normal blood treated in this way, and normal cerebro- 
 spinal fluid produce entirely negative results. 
 
THE CROONIAN LECTURES ON THE 
 
 FIG. 14. Half the original size. Effect of injecting in a cat 2'5 cc. of 
 a O'lper cent, solution of neurine. In the tracing (R.) each upstroke is caused 
 by inspiration. Note the increase in respiratory efforts followed by a 
 decrease. In the blood-pressure tracing there is a fall followed by a pro- 
 nounced rise. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 59 
 
 The next couple of tracings (figs. 10 and 11) illustrate the 
 dilating action of choline and cerebrospinal fluid respectively on 
 the peripheral blood-vessels. The upper tracing in each case is 
 that of the intestinal oncometer, rise of the lever of which indi- 
 cates dilatation of blood-vessels. 
 
 The next tracings (figs 12 and 13), show how after atropine 
 the fall of blood pressure is replaced by a rise. I give only one 
 of a pair of tracings, that obtained with choline, obtained by 
 making an extract of cat's brain ; others obtained with cere- 
 brospinal fluid are practically identical with it. 
 
 I might, however, go on multiplying graphic records co show 
 that physiologically the material obtained from cerebrospinal 
 fluid has exactly the same action as choline. But I will be 
 content with giving two more, which show how different is the 
 effect of neurine (figs. 14 and 15). The text beneath the figures 
 gives the details ; the tracings show the effect on blood pressure (a 
 rise sometimes preceded by a slight fall, cardiac in origin), on 
 respiration (exacerbation of movement), and on the intestinal 
 blood-vessels (a constriction accompanying the rise of blood 
 pressure). 
 
 The chief interest in our work has centred round the discovery 
 that the cerebrospinal fluid of patients suffering from general 
 paralysis contains toxic material. We believe that this toxic 
 material, which undoubtedly originates from the disintegration of 
 nervous tissue, is probably not a single substance. We have 
 obtained chemical evidence of the existence of nucleo-proteid in 
 the fluid, and though the amount of nucleo-proteid is not, as 
 a rule, sufficient to cause massive intravascular clotting when the 
 fluid is injected into animals, we consider that the presence of 
 even small quantities continuously being poured out into the 
 cerebrospinal fluid, collecting in the perivascular lymphatics and 
 passing thence to the blood will produce harmful results. The 
 idea has suggested itself to our minds that an increase in the 
 coagulability of the blood in the small vessels of the cerebral 
 region, which nucleo-proteid would produce, might form a deter- 
 mining factor in promoting venous stasis, and thus are caused the 
 acute manifestations or seizures of apoplectiform or epileptoid 
 nature which the patients exhibit. 
 
 The other toxic material which we have succeeded in isolat- 
 ing, namely, choline, will not account for the majority of the 
 
60 
 
 THE CBOONIAN LECTUKES ON THE 
 
 FIG. 15. Three-quarters of the original size. Effect of injecting 1 cc. of 
 a 0*1 per cent, solution of neurine. The preliminary fall of blood pressure 
 is absent in this case ; the rise is accompanied by the constriction of the 
 peripheral blood-vessels, as shown by the fall of the recording lever of the 
 intestinal oncometer (7.0. ). 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 61 
 
 symptoms of the disease. In the completeness with which we 
 have been enabled to identify (both on chemical and physiological 
 grounds) choline in the cerebrospinal fluid and blood of these 
 patients, we consider our work has been satisfactory only up to a 
 certain point. As affording a complete explanation of the path- 
 ology of the disease it has been a disappointment ; we regard the 
 fact that choline does exist in these fluids chiefly as an indication 
 of the disintegration of the brain-tissue, and if the majority of 
 the symptoms are to be explained on the basis of auto -intoxication 
 due to such disintegration, we must confess, if we except nucleo- 
 proteid, that any highly poisonous substance has eluded our 
 grasp : certainly lactic acid and glycero-phosphoric acid are not 
 very poisonous ; they are even less so than choline. 
 
 Still, even choline has some effect. A feeble circulation and 
 fatty degeneration of the heart are very frequent concomitants of 
 the terminal stages of the disease, especially after a series of 
 seizures, and the idea seemed feasible at one point in our research 
 that choline might explain these. A single dose of choline in a 
 dog or cat produces but little effect on the heart ; still there is 
 some effect, and it does not appear a far-fetched idea to suppose 
 that the continual pouring of small doses of choline into the 
 cardiac tissue might in time produce cardiac weakness, and even 
 degeneration. This possibility still remains, but our study of the 
 disease, and of the physiological action of choline, has shown us 
 that choline will not explain the fits, but rather that the fits will 
 explain the degeneration in heart and other muscles. Such fatty 
 degeneration probably never occurs unless fits have occurred 
 before death, and if similar fits occur in other diseases, as in the 
 status epilepticus of epilepsy, there is the same fatty degeneration 
 of the muscular tissues, even though no massive disintegration 
 of nervous tissues has been present. 
 
 Take again the point of enfeebled circulation ; the pulse is 
 often small and might be supposed to be associated with low 
 tension. By the use of the Hill-Barnard sphygmorneter, Dr. 
 Mott has tested this point on a large number of patients. In the 
 first and second stages of the disease (i.e., before the patient 
 becomes bed-ridden) the arterial pressure is, as a rule, higher 
 than normal ; obviously choline alone will not explain this. At 
 the beginning of epileptiform seizures the pressure is still high, 
 but after prolonged convulsions the pressure falls considerably, to 
 
62 THE CEOONIAN LECTURES ON THE 
 
 rise again a few days after the convulsions have ceased. There 
 can be no doubt that the convulsions are associated with the 
 breaking down of nervous tissue, and we therefore think it 
 probable that the choline so liberated is responsible for the fall of 
 pressure which occurs then. 
 
 Our experiments with atropine are by no means uninstructive 
 in connection with this subject. A small dose of atropine will 
 modify the action of choline and produce a high instead of a low 
 blood pressure. We do not, of course, mean to suggest that 
 atropine or even a similar alkaloid is present in these patients, 
 but these experiments do suggest that with a plurality of causes 
 we undoubtedly obtain an intermixture or even a reversal of 
 effects. No doubt with fresh light, which future work may throw 
 on our own, it may be possible to see the modus operandi of these 
 pathological processes more clearly, and our three years' work 
 will not have been thrown away if it forms some sort of guidance 
 to others, or to ourselves, in unravelling the plurality of causes 
 to which we have just alluded, and which we must assume is 
 present in General Paralysis as in so many other obscure diseases. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 63 
 
 LECTURE IV. 
 THE CHEMISTRY OF NERVE DEGENERATION. 
 
 WE have now seen that in the disease called General Paralysis 
 of the Insane, the degenerative changes that occur in the central 
 nervous system are associated with the presence of the products 
 of such degeneration in the cerebrospinal fluid. One of these 
 products, choline, is derived from the break-down of lecithin, but 
 we also noted that there are others, for instance, nucleo-proteid. 
 Choline can be identified in the blood also of these patients. 
 The tests on which one relies for the detection of this alkaloid 
 are mainly two : the first is a chemical test, namely, the obtain- 
 ing of the typical yellow octahedral crystals from the alcoholic 
 extract of the blood. These crystals have not only a definite 
 form, but their solubilities distinguish them from other somewhat 
 similar crystals, as also does the fact that they yield a fixed 
 percentage of platinum, and give rise to an odour of trimethyla- 
 rnine when decomposed by heat. The second test is a physio- 
 logical one ; a saline solution of choline, of choline hydrochloride, 
 and of the residue obtained from the alcoholic extract of the 
 cerebrospinal fluid and blood of these patients, produce a tem- 
 porary fall of pressure when injected intravenously in animals. 
 This fall is partly cardiac in origin, and partly due to dilatation 
 of peripheral blood-vessels ; the dilatation is due to the direct 
 action of the alkaloid on the neuro- muscular mechanism of the 
 blood-vessels themselves. There are many substances which 
 produce a fall of arterial pressure, but choline is peculiar in the 
 fact that after the administration of a small dose of atropine 
 subcutaneously, it no longer produces a fall but a rise of blood 
 pressure, or, at any rate, the fall is abolished. 
 
 In the investigation of the blood, as a rule, only a small 
 amount of material has been at one's disposal, and in order to 
 obtain satisfactory evidence of choline it is necessary to con- 
 
64 THE CROONIAN LECTURES ON THE 
 
 siderably concentrate the alcoholic extract. It is therefore 
 necessary to limit the number of tests to be performed. The 
 two tests, however, appear to be, if positive, absolutely conclusive 
 evidence of the presence of choline. The iodine test which has 
 been employed by some investigators is not a very delicate one, 
 especially in the presence of other organic substances. The great 
 value and delicacy of the platinum test has been emphasised in the 
 recent work of Gumprecht. 1 
 
 Although the first paper, 2 by Mott and myself, dealt principally 
 with General Paralysis, we indicated that the presence of choline 
 in large quantities in the cerebrospinal fluid is not characteristic 
 of this disease ; we mentioned that in other diseases where great 
 and evidently acute wasting of the brain tissue had occurred, 
 choline was also present in excess in this fluid. 
 
 Since the publication of our work, the subject has been taken 
 up by Gumprecht and our observations have been confirmed and 
 extended by him. We stated that in the normal fluid choline 
 was either absent or present in such small quantities that our 
 tests were not sufficiently delicate to detect it. Gumprecht has 
 shown that if sufficient fluid is employed it is possible to demon- 
 strate the presence of minute quantities of choline in it ; but this 
 is enormously increased not only in General Paralysis, but in 
 many other diseases of the nervous system ; he directed his 
 attention in particular to acute diseases like meningitis. 
 
 The presence of choline in the normal fluid is not devoid of 
 physiological interest. It shows us that, under ordinary con- 
 ditions, lecithin is in that condition of unstable chemical equili- 
 brium which is indicated by the word metabolism. It is constantly 
 breaking down, and being constantly built up afresh, and it is 
 only in diseased conditions, in which the destructive side of 
 metabolism preponderates over the constructive, that appreciable 
 quantities of the products of its disintegration are present in 
 cerebrospinal fluid and blood. 
 
 Physiological saline solution will extract a small amount of 
 choline from perfectly normal nervous tissue at the ordinary 
 temperature (see figs. 12 and 13) ; this is most apparent in 
 
 1 Gumprecht, Verhandl. der Congr. fiir innere Medicin, Wiesbaden, 1900, 
 326. 
 
 2 Phil. Trans., Series B., cxci., pp. 211-267, 1899. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 65 
 
 situations where there is most activity, namely, in the grey 
 matter. Within the last year or two numerous observers have 
 shown this, and although they differ in opinion whether choline 
 is the most important or abundant substance in such extracts, all 
 are agreed on the main point as to its actual presence (see more 
 fully, Lecture II., p. 27). 
 
 In normal blood much the same is true. In the work which 
 we have done since the publication of our first paper we have 
 devoted our attention to the blood rather than to the cerebro- 
 spinal fluid. By concentrating large quantities of normal blood 
 it is possible to show by the platinum test the presence of minute 
 traces of choline ; but in conditions in which extensive degenera- 
 tive changes occur in the central or peripheral portions of the 
 nervous system, the amount is considerably increased, and its 
 presence can be shown in small quantities of blood; such 
 quantities of normal blood yield wholly negative results. The 
 largest yield of choline in a normal animal which we have met 
 with was in a young kitten, and doubtless in young animals the 
 myelinisation of the nerve- fibres which is taking place implies 
 more active metabolism of the lecithin than in adult animals. 
 
 The general plan of our work has been (1) to examine the 
 blood in various diseases of the nervous system in man ; (2) to 
 examine the blood in animals in which degeneration of the 
 nerves has been made to occur by section of large nerves like 
 the sciatics ; (3) in these animals we have examined the nerves 
 themselves in various stages of degeneration ; this examination 
 has been partly microscopic and partly chemical, and we have 
 sought to correlate the two sets of changes, and in particular 
 have endeavoured to ascertain the chemical meaning of the 
 Marchi reaction, which is the method principally used to-day 
 for the microscopic detection of degeneration in nerve-fibres. 
 
 Before passing on to consider our experiments, observations, 
 and results in detail, it may be well at this point to again 
 briefly allude to the composition of lecithin, and to the main 
 features of the Marchi reaction. 
 
 Lecithin, the chief constituent of the medullary sheath, 
 differs from ordinary fats in containing two additional elements, 
 namely, nitrogen and phosphorus. An ordinary fat on decom- 
 position breaks up into glycerin and fatty acid. Lecithin under 
 
66 THE CROONIAN LECTURES ON THE 
 
 similar circumstances yields glycerin, fatty acid, phosphoric acid, 
 and a base called choline (C 5 H IS NO 2 ). 
 
 We have in our work endeavoured to follow the history of 
 lecithin disintegration, not only in regard to the nitrogen it 
 contains (the choline radicle), but also in respect of its 
 phosphorus. 
 
 It is probable that in the body lecithin is not present in 
 the free state, but in combination with a cerebrin or cerebrins 
 to form a still more complex substance called protagon (see 
 Lecture I., p. 10). 
 
 The Marchi reaction consists in placing small pieces of 
 nervous tissue in a mixture of osmic acid and Miiller's fluid, 
 after previous hardening in Miiller's fluid. Under these circum- 
 stances healthy nerve-fibres are stained a greenish-grey colour, 
 but degenerated nerve-fibres are stained an intense black. In 
 the later stages of degeneration, when the fatty products of the 
 decomposition of the fibres have been absorbed, this black stain- 
 ing is naturally no longer observable. It is important also to 
 observe that ordinary neutral fats, such as are contained in 
 adipose tissue, give the Marchi reaction. It was knowledge of 
 this fact that led us in part to the present investigation, and our 
 expectation has been fully confirmed that the cause of the Marchi 
 reaction in degenerated nerve-fibres is the replacement of the 
 phosphorised fat by non-phosphorised fat. 
 
 Before the commencement of our joint work, Dr. Mott 3 had 
 made some preliminary experiments in this direction, which 
 were continued in conjunction with Dr. Barratt. 4 Spinal cords 
 -on one side of which degeneration had occurred, due to a lesion 
 in the opposite cerebral hemisphere, were divided longitudinally 
 into two halves ; each half was extracted with ether in a Soxhlet's 
 apparatus. The residue of the ethereal extract from the degene- 
 rated side was more abundant, but contained less phosphorus 
 than on the healthy side ; on the healthy side the residue 
 consisted chiefly of protagon crystals. The degenerated half of 
 each cord was also more watery. 
 
 Another worker who has made experiments in the same 
 
 3 Clifford Allbutt's "System of Medicine," vol. i., "Pathology of 
 Nutrition." 
 
 * Pro. PhysioL Soc., February ; Journ. of Physiology, xxiv., p. iii. 
 
CHEMICAL SIDE OP NERVOUS ACTIVITY 67 
 
 direction is A. Noll. 3 He showed that in Wallerian degeneration 
 of peripheral nerves, the amount of protagon diminishes until 
 at last none at all is obtainable. 
 
 After these introductory remarks we may now pass to the full 
 consideration of our own results ; these may be most con- 
 veniently arranged under the following heads : 
 
 (1) Examination of the blood in cases of nervous disease in 
 man. 
 
 (2) Experiments upon animals. (a) Examination of the 
 blood in cats in which Wallerian degeneration had been pro- 
 duced by section of nerves ; (b) chemical examination of the 
 degenerated nerves ; (c) histological examination of the degene- 
 rated nerves. 
 
 (3) General conclusions. 
 
 The histological part of the work has been carried out entirely 
 by Dr. Mott. The experiments in which living animals were 
 employed were carried out entirely by myself at King's College. 
 In this part of the work cats were exclusively employed. The 
 animals were anaesthetised with the A.C.E. (alcohol, chloroform, 
 ether) mixture during the operation, and rigid antiseptic precau- 
 tions adopted. 
 
 (1) EXAMINATION OF THE BLOOD IN CASES OF NERVOUS 
 DISEASE IN MAN. 
 
 The fact that we had examined the blood from several cases 
 of General Paralysis has already been alluded to in the third 
 lecture. The blood was removed by venesection as a remedial 
 measure during seizures, and gave both the chemical and physio- 
 logical tests for choline. 
 
 We have also described 6 the results of examining in a similar 
 way the blood from a case of Beri-beri. This is a tropical 
 disease, which is accompanied by extensive degenerative changes 
 in nerves and muscles, and great vascular depression. A saline 
 solution of the residue from the alcoholic extract of the blood, 
 produced on injection a marked physiological result like that 
 caused by a large dose of choline. The amount of material at 
 our disposal did not enable us to make a thorough chemical 
 
 5 Zeitsch. f. physiol. Chem. t xxvii., p. 370, 1899. 
 
 6 British Medical Journal, July 29, 1899. 
 
68 THE OROONIAN LECTURES ON THE 
 
 examination of the blood. Using the platinum test we only 
 obtained some ill-formed crystals of a light yellow tint, which 
 we were unable to assert positively consisted of the double salt 
 of choline. 
 
 Venesection is so seldom employed as a therapeutic measure 
 that since then we have had comparatively few opportunities of 
 examining the blood removed during life. The specimens we 
 have examined are the following : 
 
 (1) Blood from a chronic case of Beri-beri. 
 
 (2) Blood from an acute case of the same disease. 
 
 (3) Blood from a case of the same disease, but we were not 
 informed whether it was acute or chronic. 
 
 In all these three cases the blood was removed during life ; 
 it was immediately mixed with excess of alcohol, and forwarded 
 to us. We have to thank Dr. Patrick Manson, F.E.S., for the 
 first two specimens, and Dr. Hamilton Wright, Director of the 
 Pathological Laboratory of the Federated Malay States, for the 
 third specimen. 
 
 (4) Blood from a case of disseminated sclerosis (early stage) 
 which was under the charge of Dr. Mott. This was removed 
 during life by venesection. 
 
 (5) Blood from a case of combined sclerosis. This was 
 removed very soon after death. W T e have to thank Dr. Batten 
 for supplying us with this specimen. 
 
 (6) Blood from a case of alcoholic neuritis, removed very 
 soon after death by Dr. Mott. 
 
 It will be seen that the diseases from which these patients 
 suffered were very various, but all possess in common the 
 feature which is also present in General Paralysis, of an exten- 
 sive degenerative change in either the central or peripheral parts 
 of the nervous system. 
 
 Before passing on to the study of the results, it will be best 
 to state rather more fully the methods adopted. 
 
 The blood was mixed with six or eight times its volume of 
 absolute alcohol, and filtered. The alcoholic filtrate was evapor- 
 ated to dryness at 40 C., and the residue taken up with absolute 
 alcohol. After filtration, the alcoholic solution was again 
 evaporated to dryness, and the residue again taken up with 
 absolute alcohol. This was repeated twice more, in order to 
 ensure the absence of potassium salts. The final alcoholic solu- 
 
CHEMICAL SIDE OF NEBVOUS ACTIVITY 69 
 
 tion was divided into two parts, A and B. Part A was used for 
 chemical examination. Part B was used for the physiological 
 test. 
 
 To part A, platinum chloride dissolved in alcohol was added, 
 and the precipitate that formed was allowed to settle, and washed 
 by decantation with absolute alcohol. It was then dissolved in 
 15 per cent, alcohol. Ifc did not all dissolve, so the platinum 
 chloride must have precipitated substances other than choline. 
 The solution was freed from the insoluble residue by nitration, 
 and then evaporated in a watch-glass to dryness at 40 G. Micro- 
 scopical examination of the watch-glass with a low power showed 
 whether or not the octahedral crystals were present, and a rough 
 quantitative estimation of the choline was made by noting 
 whether or not the crystals were abundant. Weighings were 
 made in some cases, after redissolving and recrystallising, but as 
 will be more fully explained when we come to the consideration 
 of cats' blood, we do not regard our numbers as very trustworthy. 
 For practical purposes the rougher method of a microscopic 
 survey gives excellent comparative results, provided the same 
 quantity of the original blood is taken in each case. The 
 quantity we used was 10 cc. Using this quantity, normal human 
 blood gives practically negative results, though a few occasional 
 and small octahedra can generally be discovered on careful 
 examination. 
 
 Part B was again evaporated to dryness, and the residue 
 dissolved in physiological saline solution. After filtration, the 
 solution was used for injection. It was free from proteid, but 
 was usually somewhat opalescent. We have not determined 
 what this opalescence was due to, though it appears possible 
 that it may be caused, by the presence of small quantities of 
 lecithin, derived, like its decomposition product, choline, from the 
 degenerated nervous tissue. No fat particles could be seen with 
 the microscope. The fluid had a neutral reaction. A cat was 
 then anaesthetised with A.C.E. mixture ; the carotid artery of one 
 side was connected with a mercurial kymograph for the registra- 
 tion of the arterial blood pressure. The external jugular vein of 
 the opposite side was exposed, and into this the fluid was 
 injected. The volume of fluid injected was in each case 5 cc., 
 and the amount of the original blood to which this corresponded 
 was noted. Concentration was usually carried out, so that the 
 
70 THE CROONIAN LECTURES ON THE 
 
 injection of 5 cc. corresponded to 20 or 30 cc. of the original 
 blood ; the actual amounts will be found in the letter press under- 
 neath the tracings reproduced in the subsequent pages. After 
 noting the effect of such injection, 0'5 cc. of a 0-5 per cent, 
 solution of atropine was injected subcutaneously into the cat, and 
 a few minutes allowed to elapse. In order to test whether the 
 animal was fully atropinised, the vagus of one side was stimu- 
 lated, or 2-5 cc. of a 0-2 per cent, solution of choline hydro- 
 chloride was injected into the jugular vein. When inhibition of 
 the heart by vagus stimulation was not obtained, or when 
 choline hydrochloride failed to produce its usual fall of arterial 
 pressure (or this was replaced by a rise), the experiment was 
 continued. The second part of the physiological test was then 
 performed, and consisted in again injecting the saline solution 
 from the blood suspected to contain choline. If the injection 
 now produced no fall of arterial pressure, or this fall was 
 replaced by a rise, the identification of choline by physiological 
 means was completed. 
 
 Choline was present in all the cases enumerated. The two 
 tests fitted together with great accuracy. If the chemical test is 
 performed first, one can prophesy from the amount of crystals 
 the result of the injection. If, on the other hand, the physio- 
 logical test is performed first, one can prophesy from the fall of 
 pressure whether an abundant or a scanty crop of crystals will be 
 obtained. 
 
 The case where the least result was obtained was the acute 
 case of Beri-beri ; this is what would have been anticipated. 
 Here the fall of pressure was insignificant, and the crystals 
 required searching for. The case where the best result was 
 obtained was from the Beri-beri blood received from the Malay 
 States (No. 3 in our list). Here the crystals thickly coated the 
 watch-glass, and the fall of pressure is shown in one of the 
 accompanying tracings. 
 
 The tracings which follow give some of our results in the 
 performance of the physiological test. They show the effects of 
 injecting the material from the case of Beri-beri just alluded to 
 (fig. 16), from that of combined sclerosis (fig. 20), from that of 
 disseminated sclerosis (fig. 19), and from that of alcoholic neuritis 
 (fig. 18). In the first case, also, the effect after the injection of 
 atropine is shown (fig. 17). This is typical of what occurred in all 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 
 
 71 
 
 
 \J \l v \J \1 v v 
 
 w\ 
 
 FIG. 16. The uppermost line represents the respiration taken by the 
 tambour method. The next line is the blood pressure from the carotid. The 
 next is a time tracing in seconds ; the next is the signal line, the raising of 
 which indicates the period of the injection. The lowest line is the abscissa of 
 the blood pressure. The various lines have the same meaning in all subse- 
 quent tracings. The respiration tracing is omitted in figures subsequent to 
 fig. 17. 
 
 The injection produced no effect on respiration. This is true also for 
 choline, and the similarity between these effects and those of choline on the 
 blood pressure may be seen readily if our former tracings are consulted. All 
 the tracings were taken from experiments on cats under A.C.E. mixture. All 
 read from right to left. The actual volume of saline solution of the active 
 material was in all cases 5 cc. This was injected into the external jugular 
 vein. The numbers given with each tracing indicate the volume of the 
 original blood to which tehis would correspond. 
 
 Fig. 16 represents the fall of arterial pressure produced by the injection 
 of an amount equal to 10 cc. of the blood in the case of Beri-beri numbered 
 3 in the list on p. 68. This tracing and all that follow are of the original 
 size. 
 
72 
 
 THE CROONIAN LECTURES ON THE 
 
 the fall of pressure is either absent or replaced by a slight 
 
 cases 
 rise. 
 
 With regard to the chemical test, the various watch-glasses 
 have been exhibited at meetings of the Physiological and 
 Pathological Societies, and have admittedly borne out our 
 contention. 
 
 AAAA/W 
 
 ! . . . I . . . . 
 
 FIG. 17. The result of injecting the same volume of the same solution 
 in the same cat after atropine had been administered. There is now a rise 
 of blood pressure. 
 
 These results are of some practical importance. A com- 
 paratively small quantity of blood will give the tests, and in cases 
 where it is difficult to distinguish between serious cases of organic 
 disease and cases of so-called functional neurosis, the performance 
 of the tests described may come to the assistance of the practical 
 physician in making his diagnosis. Choline does not pass into 
 the urine, 1 so that the examination of that secretion would be 
 insufficient in such cases. 
 
 Mott and Halliburton, loc. cit., p. 256. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 73 
 
 (2) EXPERIMENTS UPON ANIMALS. 
 
 In these experiments twenty cats were experimented upon. 
 In the majority of cases both sciatic nerves were divided in the 
 upper part of the thigh. During the operation the animal was 
 anaesthetised with A.C.E. mixture, and antiseptic precautions 
 rigorously adopted. Healing of the wound took place rapidly by 
 the first intention in all cases but one. In this one case suppura- 
 tion occurred, and the animal was killed three days after the 
 operation. Another cat died suddenly a few hours after the 
 operation. We have, therefore, only eighteen cats concerning 
 which we have to record results. 
 
 FIG. 18. The result of injecting an amount equal to 30 cc. of blood 
 from a case of alcoholic neuritis. 
 
 The animals suffered but little inconvenience ; they were able 
 to walk about in spite of the partial paralysis of the hind limbs ; 
 they walked on the heels of these limbs, and in consequence the 
 fur was worn off here in those animals which were kept alive for 
 sufficiently long periods. They were kept in warm comfortable 
 hutches, were well fed, and soon became well nourished and sleek 
 specimens of the feline tribe. Some wasting of the muscles of 
 the hind limbs necessarily occurred in those kept alive for the 
 longer periods. 
 
 The cut nerves were not sutured in the greater number of 
 
74 THE CBOONIAN LECTURES ON THE 
 
 cases, but union and regeneration took place in nearly all, pro- 
 vided the time which elapsed between the operation and the 
 post mortem was long enough. In one or two cases the ends of 
 the nerve of one side were sutured together with catgut. The 
 details of the individual operations and main results are as 
 follows : 
 
 FIG. 19. --Result of injecting an amount equal to 20 cc. of blood from a 
 case of disseminated sclerosis (early stage of the disease). 
 
 Cat K. One sciatic nerve only divided. The animal was' 
 killed twenty- four hours later. The peripheral end of the cut 
 nerve was stimulated mechanically and electrically ; well marked 
 contraction followed. The divided nerve was compared with the 
 
CHEMICAL SIDE OF NEKVOUS ACTIVITY 
 
 75 
 
 healthy nerve on the other side by means of faradisation, a 
 du Bois Reymond coil with one cell being used. The weakest 
 induction shock which produced a muscular response occurred 
 with the secondary coil at 27 cm. on the healthy side and 25 in 
 the case of the divided nerve. The divided nerve on subsequent 
 examination, was found to be both histologically and chemically 
 normal. 
 
 FIG. 20. Result of injecting an amount equal to 30 cc. of blood from a 
 case of combined sclerosis. 
 
 Cat A. Both nerves divided. This animal was killed five 
 days and two hours after the operation. Left nerve : muscles 
 responded with the secondary coil at 20. Right nerve : muscles 
 responded with the secondary coil at 25. The muscles on each 
 side responded readily to mechanical excitation of the nerves. 
 The nerres were practically healthy, both histologically and 
 chemically. 
 
 Cat B. Both nerves divided. This animal was killed three 
 days after the operation. Left sciatic : muscles responded with 
 
76 THE CEOONIAN LECTURES ON THE 
 
 the secondary coil at 18. Eight sciatic : muscles responded with 
 the secondary coil at 22. The response to mechanical stimulation 
 was slight. The nerves on chemical and histological examination 
 show but little sign of degeneration. 
 
 Cat P. Both nerves divided. This animal was killed three 
 days and twenty hours after the operation. There was no 
 muscular response on stimulating either nerve. Signs of com- 
 mencing degeneration are evident. 
 
 Cat C. Both nerves divided. This animal was killed four 
 days and three hours after the operation. No response occurred 
 on either side on stimulation. Signs of early stages of Wallerian 
 degeneration are seen. 
 
 Cat E. Both nerves divided. This animal was killed five 
 days after the operation. In this animal no muscular response 
 occurred on excitation of either nerve ; and the same is true for 
 the animals that were killed at later stages, until union and 
 regeneration has taken place. Degenerative changes in the 
 nerves are more marked. 
 
 Cat D. Both nerves divided. This animal was killed six 
 days after the operation. Degenerative changes in the nerves are 
 about the same as in Cat E. 
 
 Cat I?. Both nerves divided. This animal was killed eight 
 days after the operation. 
 
 Cat N. Both nerves divided. This animal was killed ten 
 days after the operation. 
 
 Cat Q. Both nerves divided. This animal was killed thirteen 
 days after the operation. In these three animals (E, N, Q) the 
 degenerative change is extremely well seen by the Marchi 
 method. 
 
 Cat J. Both nerves divided. This animal was killed twenty- 
 five days after the operation. 
 
 Cat 0. Both nerves divided. This animal was killed twenty- 
 seven days after the operation. 
 
 Cat W. Both nerves divided. The left nerve was sutured 
 with catgut. This animal was killed twenty-nine days after the 
 operation. 
 
 In these three cats (J, O, W) there was considerable wasting 
 of the muscles supplied by the sciatics. Union of the divided 
 nerves had occurred in all cases, but they were all irresponsive to 
 stimulation. Little or no difference could be detected histologi- 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 77 
 
 cally or chemically in the two nerves of Cat W, one of which 
 had been sutured. The Marchi reaction was still well marked, 
 but there was evidence that absorption of the fatty products of 
 degeneration was in progress. Phosphorised fat had almost, and 
 in the case of Cat W entirely, disappeared. 
 
 Cat H. Both nerves divided. This animal was killed forty- 
 four days after the operation. Good union had occurred on both 
 sides, but the nerves were irresponsive to stimulation. Degenera- 
 tion had now advanced so far that there was almost complete 
 removal of the products of degeneration. There are early signs 
 of regeneration. Here also the wasting of muscles was very 
 evident. 
 
 Cat T. Both nerves divided ; left sutured with catgut. 
 This animal was killed forty-five days after the operation. In 
 this animal for the few days preceding its death the paralysis 
 was less marked on the sutured side. 
 
 The lef fc (sutured) nerve responded to stimulation (secondary 
 coil at 7'5 cm. ) ; the right nerve did not respond. Examination 
 of the left nerve showed early signs of regeneration ; the right 
 did not. We, however, found it difficult at this stage, or even 
 in Cat S (sixty days after operation) to trace axis cylinders 
 actually through the cicatricial tissue at the junction, although by 
 the Stroebe method axis cylinders were found in the peripheral 
 stump. A chemical examination of these nerves was unfortu- 
 nately omitted. 
 
 Cat S. Both nerves divided. This animal was killed sixty 
 days after the operation. The right nerve had not joined up 
 well ; the left not at all. The right nerve responded to stimula- 
 tion (secondary coil at 9) ; the left did not. The evidence of 
 regeneration was not so manifest as in the last case, and the 
 products of degeneration had not undergone so much absorption. 
 This animal displayed much lethargy, and was ill nourished, as if 
 it lacked vital reaction. 
 
 Cat I. Both nerves divided. This animal was killed one 
 hundred days after the operation. 
 
 Cat F. Both nerves divided. This animal was killed one 
 hundred and six days after the operation. 
 
 In these two cats (I and F) though the hind limbs were still 
 thin, there was great recovery of function. The nerves responded 
 well to both mechanical and electrical stimulation (secondary coil 
 
78 THE CROONIAN LECTURES ON THE 
 
 at 16 to 18 cm.). The nerves, especially the sensory ones, 
 showed well-marked regeneration, and chemically they had 
 returned approximately to the normal state. 
 
 These results may be briefly summarised in the following way. 
 Up to the third day the nerves remained excitable and approxi- 
 mately normal. Degenerative changes then set in and became 
 well marked on the eighth day ; from this time to the thirteenth 
 day they were at their height. On the twenty-fifth day, and at 
 periods later than this, union of the divided nerves had nearly 
 always taken place. The twenty-ninth day marks the entire 
 disappearance of phosphorus from the degenerated fat. Absorp- 
 tion and removal of the fat was nearly accomplished by the 
 forty-fourth day. At the same period restoration of function 
 began in the case of a sutured nerve ; but where the nerves had 
 not been sutured this was not seen until the sixtieth day. In the 
 cats which were allowed to live one hundred days and longer, 
 regeneration and restoration of function were well marked. 
 
 A point of some interest is the early date (44-45 days) at 
 which the removal of degenerated products occurs in peripheral 
 parts of the nervous system. In this there is a contrast to the 
 central nervous system ; there the Marchi reaction can be 
 obtained in degenerated tracts many months after the lesion has 
 occurred. 
 
 The further experiments performed in connection with these 
 animals divide themselves into three sets. 
 
 (a) Experiments with the blood. 
 
 (b) Chemical examination of the nerves. 
 
 (c) Histological examination of the nerves. 
 
 (a) EXPERIMENTS WITH THE BLOOD OP THE CATS. 
 
 These may be very briefly stated. The methods adopted 
 were the same as those already described in connection with 
 human blood. 
 
 The blood of normal cats contains the merest traces of choline. 
 A few crystals can generally be found by the platinum test. As 
 stated at the commencement of this lecture, the most abundant 
 yield from a normal animal was obtained from the blood of a 
 young kitten. But the quantity was not sufficient to give, with 
 the amount injected, the physiological test. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 
 
 79 
 
 When signs of degeneration set in (fourth day) the quantity 
 of choline in the blood increased. As with human blood, the 
 chemical and physiological tests gave throughout corresponding 
 results. The best yield of crystals, and the most marked fall of 
 blood pressure we obtained was in the case of the eight-day cat. 
 This fall was abolished by atropine. On the thirteenth day there 
 
 FIG. 21. Result of injecting an amount equal to 20 cc. of blood of 
 normal kitten. 
 
 was still a marked positive result. From this time onwards the 
 evidence of choline steadily diminished, until the normal was 
 reached in the later stages of the degenerative process. The 
 amount slightly increased when regeneration set in, and this is 
 another piece of evidence in favour of the views already advanced 
 concerning lecithin metabolism (see p. 26). 
 
80 THE CBOONIAN LECTURES ON THE 
 
 I select a few tracings to illustrate these facts. 
 
 It will be seen that the material from normal blood (fig. 21), 
 from blood of an animal in which degeneration had not com- 
 menced (fig. 22), and from blood of an animal in which degenera- 
 tion was complete (fig. 29), gave negative results. 
 
 In cases where degeneration had set in (blood of six-day cat, 
 fig. 23), or had commenced to subside (twenty-five-day cat, 
 fig. 28), the effect was slight. 
 
 FIG. 22. Result of injecting an amount equal to 20 cc. of blood obtained 
 from Cat A (two days after section of both sciatic nerves). 
 
 In the case of the cats where degeneration was at its height, 
 the physiological effect, fall of blood pressure, was very marked 
 (figs. 24 and 26), and the fall was absent after atropinisation 
 (figs. 25 and 27). This was true in all cases ; wherever the 
 material produced a fall of blood pressure before the subcutaneous 
 injection of atropine, it failed to do so afterwards, or even pro- 
 duced a slight rise. This, in conjunction with the chemical test, 
 conclusively proved the presence of choline. The slight effects 
 obtained when regeneration set in were about equal to those seen 
 in figs. 23 and 28. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 81 
 
 As in the case of human blood, we attempted to make some 
 quantitative estimation of the amount of choline present, by 
 recrystallising the platinum salt and weighing it. We do not 
 regard our figures as very trustworthy, for the following 
 reasons : 
 
 (1) Control experiments with pure choline in organic mixtures 
 gave very variable results ; (2) the choline in our specimens was 
 
 FIG. 23. Result of injecting an amount equal to 20 cc. of blood obtained 
 from Cat D (six days after section of both nerves). 
 
 mixed with small quantities of other organic substances ; (3) the 
 numbers obtained are so small, that extremely minute errors 
 (i.e., legitimate errors of experiment) will make comparatively 
 large variations. The amount of blood at our disposal for such 
 experiments seldom exceeded 50 cc., and was usually less than 
 this. For this reason, we have relied upon the rougher method 
 of a microscopic survey of the watch-glasses as explained on 
 p. 69. This method hardly appeals to those who read about it 
 
 6 
 
82 THE CROONIAN LECTURES ON THE 
 
 like a table of quantitative estimations, but it is very convincing 
 to those who actually see the preparations. 
 
 With this reservation, we may say that the method of 
 quantitative analysis gave us, in the cats the blood of which 
 contained most choline, numbers which corresponded to a per- 
 centage of from 0-0052 to 0-0078. In the animals in which the 
 chemical and physiological tests indicated a low percentage of 
 choline, the corresponding numbers varied from O'OOll to 0-0037. 
 
 FIG. 24. Result of injecting an amount equal to 30 cc. of blood obtained 
 from Cat R (eight days after section of both nerves). 
 
 (b) CHEMICAL EXAMINATION OF THE CATS' NERVES. 
 
 The nerves were carefully dissected out, weighed, dried to 
 constant weight at 110 C., and again weighed. The dry residue 
 was used for the determination of phosphorus. Considering the 
 small weight of the nerves, we judged this would give more 
 accurate results than any attempt to isolate the fatty material, 
 -and determine either the phosphorus or protagon in that. 
 
 The dried nerve was soaked in 5 per cent, hydrochloric acid 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 83 
 
 for three weeks in order to get rid of inorganic phosphates. Such 
 treatment apparently gets rid of the phosphorus combined as 
 nuclein or nucleo-proteid ; for in many of the nerves of later 
 date there was considerable nuclear .proliferation seen micro- 
 scopically, and yet little or no phosphorus was obtained from the 
 nerves after treatment in this way with hydrochloric acid. The 
 
 FIG. 25. Result of injection of the same amount after atropine. 
 
 phosphorus we did obtain came, therefore, either wholly or 
 chiefly from the phosphorised fat (lecithin or protagon). The 
 nerves were then dissolved on the water bath at 100 C. in 
 fuming nitric and sulphuric acids, to which an occasional pinch 
 of potassium chlorate was added. The heating with acid was 
 continued for many hours. The phosphate so formed was pre- 
 cipitated by ammonium nitro-molybdate. The yellow precipitate 
 so obtained was washed, and dissolved in dilute ammonia, then 
 precipitated by magnesia mixture ; this precipitate was incinerated 
 and weighed as magnesium pyrophosphate. 8 
 
 8 A full description of this method of phosphorus estimation is given in 
 the Journ. of Physiology, xiii., pp. 814, 821, 1892. 
 
84 THE CROONIAN LECTURES ON THE 
 
 The following tables give the results : 
 
 TABLE X. 
 PROPORTION OP WATER AND SOLIDS IN SCIATIC NERVES OP NORMAL CATS. 
 
 Percentages 
 Water Solids 
 
 Cat 1 66-479 33-521 
 
 ,,2 65-803 34-197 
 
 ,,3 66-554 33-446 
 
 , 4 62-559 37-441 
 
 Average 
 
 65-349 
 
 34-651 
 
 TABLE XI. 
 
 PROPORTION OP WATER AND SOLIDS IN SCIATIC NERVES FROM CATS 
 OPERATED ON, IN WHICH THE NERVES WERE STILL EXCITABLE. 
 
 Percentages 
 
 Cat K. 1 day after operation . . 
 ,, A. 2 days, 5 hours after operation 
 ,, B. 3 days after operation . . 
 
 Average 
 
 Water 
 64-199 
 
 Solids 
 35-801 
 
 64-618 35-185 
 
 64-507 35-493 
 
 TABLE XII. 
 
 PROPORTION OP WATER AND SOLIDS IN SCIATIC NERVES FROM CATS 
 OPERATED ON, IN WHICH DEGENERATION OCCURRED. 
 
 Percentages. 
 
 Cat P. 
 
 C. 
 
 B. 
 
 N. 
 Q. 
 J- 
 O. 
 
 ., w. 
 
 ,, s, 
 
 3 days, 20 hours after operation 
 
 4 days after operation 
 5 
 
 6 
 
 8 
 10 
 13 
 25 
 27 
 29 
 
 44 
 60 
 
 right nerve (joined 
 
 spontaneously) 
 left nerve (sutured) 
 
 left nerve (not 
 united well) 
 
 Water 
 
 Solids 
 
 73-941 
 
 26-059 
 
 68-018 
 
 31-982 
 
 69-325 
 
 30-675 
 
 68-231 
 
 31-769 
 
 70-718 
 
 29-282 
 
 71-257 
 
 28-743 
 
 67-886 
 
 32-114 
 
 72 141 
 
 27-819 
 
 72-505 
 
 27-495 
 
 72-601 
 
 27-399 
 
 72-641 
 
 27-359 
 
 72-646 
 
 27-354 
 
CHEMICAL BIDE OF NERVOUS ACTIVITY 85 
 
 TABLE XIII. 
 
 PBOPOBTION OF WATER AND SOLIDS IN SCIATIC NERVES PROM CATS 
 OPERATED ON, IN WHICH REGENERATION HAD COMMENCED. 
 
 Percentages. 
 
 Water Solids 
 
 Cat S. 60 days after operation. Bight nerve. 72-645 27 '354 
 Early stage of regeneration 
 
 I. 100 days after operation. Regeneration 63-853 36-147 
 
 well marked 
 F. 106 days after operation. Regeneration 68-531 31-469 
 
 well marked 
 
 Average of I. and F 66-192 34-308 
 
 FIG. 26. Result of injecting an amount equal to 25 cc. of blood obtained 
 from Cat N (ten days after section of both nerves). 
 
86 
 
 THE CROONIAN LECTURES ON THE 
 
 From these four tables we see that, as far as water and 
 solids are concerned, before degeneration sets in there is no 
 marked change in the proportion ; the slight difference between 
 Tables X. and XI. comes well within the limits of individual 
 variation in normal cats. If we compare these with the cats 
 
 FIG. 27. Result of injection of same amount after atropine. 
 
 killed later there is a marked rise in the percentage of water, 
 and this rise advances in the main pan passu with the progress 
 of the degenerative state (Table XII.). But after restoration 
 of function (Cats I and F, Table XIII.) the proportion of wa!:er 
 to solids returns approximately to normal. 
 
 We now come to the phosphorus estimations. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 
 
 87 
 
 TABLE XIV. 
 CATS' SCIATIC NERVES. 
 
 Animal 
 
 Weight in grammes of 
 Days after section 
 
 Yield in 
 grammes 
 of 
 
 Phosphorus 
 per cent, 
 in 
 dry tissue 
 
 Fresh 
 
 Dry 
 
 Cat 1 
 Cat 2 
 
 Normal ' i rrno 
 
 0-620 
 
 0026 
 
 1-16 
 
 - 1-793 
 
 A. 
 
 2" '.'. .. ) 
 
 
 
 
 B. 
 
 3 [ 3-297 
 
 1-007 
 
 0-035 
 
 0-97 
 
 P. 
 
 3 days 20 hours . . . . j 
 
 
 
 
 C. 
 E. 
 D. 
 
 4 . ) 
 
 1-1247 
 
 0-039 
 
 0-97 
 
 5 [ 3-594 
 
 6 .' j 
 
 R. 
 
 8 | 1-193 
 
 0-379 
 
 0-0078 0-57 
 
 N. 
 
 10 . ' 1-185 
 
 0-348 
 
 0-004 0-32 
 
 
 13 .. 1-79 
 
 0-5145 
 
 0-005 0-27 
 
 
 J. 
 
 25 ! 1-655 
 
 0-5315 
 
 traces 
 
 0. 
 
 27 1*215 
 
 0-338 
 
 traces 
 
 W. 
 
 29 Right nerve' joined spon- 0'478 
 
 0-1314 
 
 
 
 
 
 
 taneously 
 
 
 
 
 
 Left nerve sutured . . 502 
 
 0-1375 
 
 
 
 
 
 H. 
 
 44 1-272 
 
 0-348 
 
 
 
 
 
 S. 
 
 60 Left nerve not joined . . 0-505 
 
 0-139 
 
 
 
 
 
 
 Right nerve, regeneration -393 
 
 0-1075 
 
 0-0003 
 
 0-08 
 
 
 beginning 
 
 
 
 
 I. 
 F 
 
 ' I 2-161 
 
 0-741 
 
 0-045 
 
 0-93 
 
 This table shows that in the early stages of degeneration the 
 amount of phosphorus is not far removed from the normal. It 
 is on the eighth day, when the Marchi reaction becomes well 
 marked, that the first great drop in the percentage of phosphorus 
 occurs. It continues to diminish and has practically disappeared 
 by the twenty-fifth, and absolutely by the twenty-ninth day. 
 With signs of commencing restoration of function it reappears, 
 and is near the normal in the last two cats where regeneration 
 had occurred. 
 
 We have confined our observations to the peripheral parts of 
 the nerves. 
 
 9 Noll (loc. cit.) in some of his experiments examined the central stump 
 of the divided nerve. He was able to perform some of his work on large 
 animals (horses), and so could obtain sufficient material from the central 
 end for analysis. Corresponding to what is termed "disuse atrophy" he 
 found some diminution in the amount of protagon in this region, but the 
 lessening was not so marked as in the peripheral end of the nerve. In the 
 
OO THE CEOONIAN LECTUBES ON THE 
 
 We can now pass on to the histological side of the subject, 
 after which we shall be better able to correlate our facts and 
 draw general conclusions. 
 
 FIG. 28. Result of injecting an amount equal to 25 cc. of blood from 
 Cat J (twenty-five days after section of both nerves). 
 
 (c) HISTOLOGICAL EXAMINATION OF THE CATS' NEBVES. 
 
 Portions of motor and sensory branches of the peripheral 
 portion of the cut nerves were in each case taken for micro- 
 
 majority of his experiments he estimated protagon, not phosphorus as we have 
 done. He puts the date of disappearance of the phosphorised fat at twenty- 
 eight days. This date and many other of his facts fit in very well with our 
 work. 
 
CHEMICAL SIDE OP NERVOUS ACTIVITY 
 
 scopic investigation. In the cases where union had occurred, 
 the junction was also reserved for the same purpose. 
 
 Each piece of nerve was pinned out across a cork frame, so 
 that the tissue was entirely surrounded by fluid. 
 
 They were placed (a) in Marchi's fluid; (b) in Miiller's 
 fluid. 
 
 FIG. 29. Result of injecting an amount equal to 25 cc. of blood from 
 Cat H (forty-four days after section of both nerves). 
 
 Portions of the former were used for teasing, and for sections, 
 transverse and longitudinal. Portions of the latter were used 
 for teasing and for sections ; portions also were, after ten days, 
 placed in Marchi's fluid, but the results obtained by this method 
 differed in no essential way from those obtained by placing the 
 nerve into Marchi's fluid direct. This simple method of placing 
 the nerve directly into Marchi's fluid enables one to obtain speci- 
 
90 
 
 THE CEOONIAN LECTUEES ON THE 
 
 mens within a week, but it is not applicable to the central 
 nervous system. 
 
 The result, comparing the two methods, may be stated in 
 tabular form as follows : 
 
 
 Nerve-fibres 
 
 White matter of 
 central nervous system 
 
 Healthy 
 
 Degenerated 
 
 Healthy 
 
 Degenerated 
 
 1. MABCHI direct 
 
 2. MARCHI after 
 MULLER 
 
 Dark greyish 
 green 
 
 Greyish green, 
 but not quite 
 so dark 
 
 Black ; adi- 
 pose tissue 
 takes the 
 same coloui 
 Black 
 
 Black on surface; 
 the fluid does not 
 penetrate well to 
 the interior 
 Greeni sh all 
 through 
 
 Black 
 Black 
 
 In order to use the Marchi reaction for the central nervous 
 system, it is essential to harden first in Miiller's fluid, for the 
 healthy nerve-fibres, unprotected as they are by a primitive 
 sheath, would stain black if placed directly into Marchi's fluid. 
 
 The actual colour obtained by the direct Marchi . method is 
 seen in the coloured plates appended. Plate II. represents the 
 condition of the nerve in transverse section, which was obtained 
 from a cat two days after the operation of cutting the nerve. 
 The fibres were healthy, the greyish green colour of the medul- 
 lary sheath is seen, and the axis cylinder with its tubular 
 fibrils can also be distinguished. Plate III. represents the stain- 
 ing obtained from a cat's nerve ninety-two hours after the 
 operation ; mixed with numerous fibres which still take on 
 the normal appearance, are others in which the myelin ring is 
 black ; a few are black all through ; evidently here the axis 
 cylinder has raptured and retracted, leaving the nerve tube filled 
 with a lump of degenerated fat. The individual fibrillae of the 
 axis cylinder can no longer be made out in any fibre. In Plate IV. 
 (nerve from an animal ten days after the operation) the degenera- 
 tive condition is much more marked. In this case the phos- 
 phorus obtained on analysis had sunk to about a quarter of the 
 normal. In the drawings, some fat cells of the surrounding 
 adipose tissue are included ; they take a deep black colour in all 
 cases, exactly similar to the colour of the thoroughly degenerated 
 fibres. 
 
 These drawings have been made in colour, because the 
 
PLATE II. Transverse section of nerve, two days after operation (Cat A). 
 Direct MARCHI method. 425 diameters. 
 
PLATE III. Transverse section of nerve, 92 hours after operation (Cat P). 
 Direct MARCHI method. 425 diameters. 
 
PLATE IV. Transverse section of nerve, 10 days after operation (Cat N). 
 Direct MARCHI method. 425 diameters. 
 

PLATE V. 
 
 FIG. 30. 
 
 FIG. 31. 
 
 FIG. 32. 
 
 FIG. 33. 
 
 FIG. 30. Transverse section of motor nerve, 53 hours after operation 
 (Cat A). Method MAKCHI'S fluid direct. The photograph is printed darkly 
 to show tubular structure of the fibrils of the axis cylinder. 700 diameters. 
 
 FIG. 31. Transverse section of nerve, 
 Same method. 500 diameters. 
 
 days after operation (Cat B). 
 
 FIG. 32. Same nerve in longitudinal section. Same method. 600 
 diameters. 
 
 FIG. 33. Longitudinal section of nerve, 92 hours after operation (Cat P). 
 Same method. 700 diameters. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 91 
 
 photo-micrographs by which the remainder of the paper is illus- 
 trated, hardly show the difference of tint in healthy and degene- 
 rated tissues ; much here depends on the depth of the printing ; 
 still, in marked cases the difference is seen even here. 
 
 Teased specimens from the nerves hardened by both methods 
 were stained with logwood and eosin and mounted in Farrant's 
 solution. 
 
 The sections were cut after imbedding in paraffin. The 
 sections were 10 p- in thickness. Both transverse and longi- 
 tudinal sections were mounted in series. Some of these were 
 stained by the Stroebe method, others with logwood and eosin, 
 and others by the Marchi-Pal method The great majority of 
 the observations, however, were made on the sections obtained 
 after hardening in Marchi's fluid direct, without extraneous 
 staining. 
 
 It is obviously impossible to describe all the microscopic 
 specimens we have made. The main results of the examination 
 have been stated already on pp. 74-77. We have made photo- 
 micrographs of our most typical specimens ; some of these are 
 here reproduced, and our object will be attained if we devote our 
 description of results mainly to these. They show the different 
 stages in the degenerative process. 
 
 Cat A. Nerves removed fifty-three hours after the operation. 
 The nerves in either transverse or longitudinal section show no 
 departure from the normal. With Marchi's fluid the medullary 
 sheath takes on the greyish-green colour before alluded to. In 
 transverse section (fig. 30, Plate V.) the tubular character of the 
 fibrils of the axis cylinder 10 is shown. 
 
 This photo-micrograph is darkly printed to show this point : 
 the myelin sheaths are not really so dark as the print would 
 indicate (see coloured drawing, Plate II.). 
 
 Gat B. Nerves removed seventy-two hours after the opera- 
 tion. The accompanying figures (figs. 31 and 32, Plate V.) 
 represent respectively transverse and longitudinal sections of a 
 motor nerve. It will be remembered that this nerve was still 
 excitable, and its percentage of phosphorus approximately 
 normal. In longitudinal section no change is observable ; in 
 transverse section the myelin rings are seen to be for the most 
 
 10 See Schafer, " Quain's Anatomy," Tenth Edition, 1891, vol. i., part 2, p. 311. 
 
92 THE CEOONIAN LECTURES ON THE 
 
 part crinkled in outline, but still stain greyish-green ; the well- 
 defined tubular character of the fibrillae of the unstained axial 
 core is no longer visible. 
 
 Cat P. Nerves removed ninety-two hours after the operation. 
 Fig. 33, Plate V., represents a longitudinal section of a motor 
 bundle. There is here breaking up of the my elm sheath into 
 short segments of irregular length ; this sheath is stained a 
 blackish colour, and in some cases the whole fibre appears either 
 completely or partially filled with the same material. The axis 
 cylinder can be seen here and there broken across and retracted ; 
 this allows the rnyelin droplet to fill the tube in these situations. 
 The degenerated fatty matter, where the change is most intense, 
 stains just like the fat cells of the surrounding adipose tissue. 
 This is obviously the beginning of the chemical change, though 
 the loss of phosphorus could not be detected chemically, partly 
 because of a considerable admixture with nerve-fibres whose 
 sheath still takes the greyish-green colour of the normal state ; 
 these appear lighter in the print. All shades between this and 
 the deep black are also seen. It is also possible that though 
 the dissociation of the phosphorised constituent of the fat has 
 taken place in the degenerated fibres, the removal of the phos- 
 phoric acid does not occur immediately after dissociation. 
 
 The nerves in this animal were not excitable. 
 
 On referring to the table of analyses (Table XII., p. 84) it will 
 be noted that the increase of water was in this case a very 
 marked feature. The explanation of this is well seen in the 
 transverse section (Plate III.), the separation of fibres from one 
 another by fluid, and the increased size of the lymph channels 
 and spaces, are very well shown. 
 
 Cat C. Nerves removed four days, three hours after opera- 
 tion. The changes are very similar to those just described ; the 
 breaking up of the medullary sheath is somewhat more pro- 
 nounced in certain fibres, whereas in others it is not (see longitu- 
 dinal section, fig. 34, Plate VI.). 
 
 Cats E and D. Nerves removed five and six days respectively 
 after operation. The nerves are but little different from those of 
 Cat C. Comparative results in different animals with different 
 resisting power are obviously difficult to make, but if anything 
 the sections examined show less degenerative change in Cat D 
 (six days) than in Cat E (five days). 
 
PLATE VI. 
 
 FIG. 34. 
 
 FIG. 35. 
 
 FIG. 36. 
 
 FIG. 37 
 
 FIG. 34. Longitudinal section of nerve, 99 hours after operation (Cat C). Method 
 MAECHI'S fluid direct. 600 diameters. 
 
 FIG. 35. Transverse section of nerve, 8 days after operation (Cat B). MULLEE'S then 
 FLEMMING'S solution. 700 diameters. 
 
 FIG. 36. Same nerve in longitudinal section. Same method. 450 diameters. 
 
 FIG. 37. Single fibre from nerve of same animal, to show multiplication of nuclei of 
 the primitive sheath. Teased specimen ; hardened in MULLEE'S fluid, washed, stained 
 with logwood, mounted in FAEEANT'S solution. 870 diameters. 
 
PLATE VII. 
 
 Wit 
 
 FIG. 39. 
 
 FIG 40. 
 
 FIG. 38. Longitudinal section of nerve, 10 days after operation (Cat N). 
 Method MARCHI'S fluid direct. 600 diameters. 
 
 FIG. 39.- Longitudinal section of nerve, 27 days after operation (Cat 0). 
 Same method. 500 diameters. 
 
 FIG. 40. Longitudinal section of nerve from same cat. Method 
 MARCHI'S fluid direct, then logwood. 450 diameters. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY \)6 
 
 Cat B. Nerves removed eight days after operation. Here 
 there is a very marked increase in the degenerative change. The 
 transverse and longitudinal sections (figs. 35 and 36, Plate VI.) 
 show hardly a fibre which in some part of its course does not 
 take on the black stain. The enlargement of the lymphatic 
 channels is also marked. On referring to Table XIV. (p. 87) 
 it will be seen that at this stage occurred the first great fall in the 
 percentage of phosphorus. It had sunk to half the normal. 
 Further evidence that not only dissociation of the lecithin molecule 
 into its constituent parts, but also removal of the products of such 
 change had begun to occur, is derived from the fact that at this 
 date most choline was found in the blood (see tracing, fig. 24). 
 Up to this point increase in the nuclei of the neurilemma had 
 been looked for without success. It was now seen very well (see 
 fig. 37, Plate VI.). It rather looks as though this increase in the 
 nuclei was the result of the irritation of the presence of degene- 
 rative products. 
 
 Cat N. Nerves removed ten days after the operation. The 
 degenerative change is still better marked. The accompanying 
 photo-micrograph (fig. 38, Plate VII.) speaks for itself. A trans- 
 verse section of this nerve is shown in the coloured drawing 
 (Plate IV.). 
 
 The percentage of phosphorus has here sunk to 0'32, or about 
 a quarter of the normal. 
 
 Cat Q. Nerves removed thirteen days after the operation. No 
 noteworthy change has occurred in the microscopic appearances. 
 The percentage of phosphorus has sunk to 0-27. 
 
 Cat 0. Nerves removed twenty- seven days after the opera- 
 tion. Here there is still considerable evidence of the Marchi 
 reaction ; the black staining of the degenerated myelin is pre- 
 cisely the same as that of the cells of adipose tissue which also 
 appear in the photo -micrograph (fig. 39, Plate VII.). 
 
 The products of degeneration have, however, been either 
 wholly or in part removed by absorption, for practically no 
 phosphorus could be obtained on analysis, and the blood was by 
 this date almost free from choline (see tracing, fig. 28). But 
 a new point is here seen, for the fat is also beginning to be 
 absorbed, and the part played in its removal by the phagocytic 
 action of certain cells is illustrated in fig. 40, Plate VII. Whether 
 the cells which are seen there crowded with the fat particles are 
 
94 THE CKOONIAN LECTURES ON THE 
 
 in part phagocytes we are unable positively to state, but we are 
 inclined, from a careful study of our specimens, to take the view 
 that they are mainly neurilemmal in origin. 
 
 Cat H. Nerves removed forty-four days after the operation. 
 Here the process of absorption is all but complete. The whole 
 nerve bundle has shrunken, and little but the sheaths, either 
 empty or filled with undifferentiated material, is to be seen. A 
 few black-staining fat droplets are still visible, and in some 
 bundles are even fewer than in the one represented in the photo- 
 micrograph (see fig. 41, Plate VIII.). 
 
 Some of the enlarged cells of the primitive sheath still 
 contain fat granules (varying from 1 to 0*7 /* in diameter), but 
 the majority are free from these, and present the elongated 
 appearance shown in fig. 42, Plate VIII. The possibility that 
 they may form an important factor in regeneration will be dis- 
 cussed later. At this date additional evidence of the complete- 
 ness of the removal of the degenerated products is derived 
 from the chemical examination of the nerves, which contained 
 no phosphorus whatever. 
 
 The figures here given (41 and 42) are from a motor branch 
 of the nerve ; the sensory branches have practically the same 
 appearances, but in transverse sections stained with Van 
 Giessen's fluid many very minute tubes can be seen with 
 central axis cylinders. 
 
 Cat F. Nerves removed 106 days after the operation. We 
 take this as an instance of a case where regeneration of structure 
 and return of function had occurred. At this date chemical 
 examination revealed the return approximately to the normal 
 condition, the percentage of water has fallen, and that of phos- 
 phorus has now risen to 0*93. The accompanying photo- 
 micrographs were all taken from a sensory branch, for here 
 regeneration had advanced further than in the motor fibres. 
 
 The new fibres are small but myelinated. Figs. 43 (Plate 
 VIII.) and 44 (Plate IX.) show them in longitudinal and trans- 
 verse section respectively. The myelin takes on the greenish- 
 grey colour of normal fibres, but the small size of the fibres (1 to 
 5 /* in diameter) will be appreciated by comparing the figures 
 with those in fig. 30 (Plate V.), the amount of magnification (700 
 diameters) being the same in both cases. Fig. 45 (Plate IX.) 
 is from a section stained by Stroebe's method to show the 
 
PLATE VIII. 
 
 FIG. 41, 
 
 FIG. 42. 
 
 FIG. 43. 
 
 FIG. 41. Transverse section of nerve, 44 days after operation (Cat H). 
 Method MABCHI'S fluid direct. 200 diameters. 
 
 FIG. 42. Nerve from same cat. Teased preparation, stained with logwood 
 and mounted in FARRANT. 500 diameters. 
 
 FIG. 43. Longitudinal section of sensory nerve, 106 days after operation 
 (Cat F). Method MARCHI'S fluid direct. 700 diameters 
 
PLATE IX. 
 
 FIG. 44. 
 
 FIG. 45. 
 
 FIG. 46. 
 
 FIG. 47. 
 
 FIG. 44. Transverse section of the same. Same method. TOO diameters. 
 
 FIG. 45. Transverse section of the same, stained by STBOEBE'S method. 700 
 diameters. 
 
 FIG. 46. Teased preparation of the same. Stained with logwocd ; mounted in 
 FABBAKT. 600 diameters. The apparent excrescences on the fibre are air bubbles 
 accidentally entangled in the FABBANT'S solution. 
 
 FIG. 47. Teased preparation of the same. Stained with logwood ; mounted in 
 FABBAKT. CO diameters. 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 95 
 
 axis cylinders. Here the outer sheath is seen to be frequently 
 thickened on one side ; this is no doubt due to the section having 
 gone through a nucleus of an interned al cell of the neurilemma. 
 
 The isolated nerve-fibres in teased preparations (figs. 46 and 
 47, Plate IX.), present some puzzling features. The new axis 
 cylinder is well seen in fig. 47, but it will be noticed that its 
 contour is uneven, some parts being distinctly thicker than 
 others. In fig. 46 it almost appears as though the elongated, 
 spindle-shaped nuclei of the primitive sheath (previously seen in 
 an earlier stage in fig. 42 (Plate VIII.) were joining up to form the 
 basis of the new axis cylinder. We do not by any means commit 
 ourselves to the view that this is what really occurs. Such a 
 view would upset previous work, showing that the axis cylinder 
 is essentially the branch of a nerve cell growing distal-wards, and 
 it would require much more evidence to prove the contrary than 
 our preparations afford. The manner of regeneration is, after 
 all, only a side issue of the main purpose of our present work, 
 which has been to correlate the histological with the chemical 
 features of the degeneration process. At some future time we 
 may return to this other equally important problem. 
 
 We will be content with saying that we think our prepara- 
 tions prove that the manifest activity of the neurilemmal cells is 
 related in some degree (perhaps nutritional if not formative) to 
 the process of regeneration ; we may also recollect that in situa- 
 tions where no neurilemma exists regeneration does not occur, 
 namely, in the central nervous system. 
 
 We can also see that the appearances to which we have just 
 called attention are capable of another interpretation ; for the 
 elongating and apparently contiguous nuclei, as seen in fig. 46, 
 may be situated outside the axis cylinder altogether, and conceal 
 it underneath or within them. The transverse section (fig. 45) 
 would support this idea. Again in fig. 47, where the central 
 strand is evidently the axis cylinder, the varicose condition 
 observed may be a natural condition of the axis cylinder, and 
 accords with the description of earlier writers, who have drawn 
 attention to enlargements on the course of an axis cylinder, and 
 to varicosities of its constituent fibrillae. 
 
 (3) GENERAL CONCLUSIONS. 
 
 Our previous work had shown us that in degenerative diseases 
 of the central nervous system, evidence of the breakdown of the 
 
96 THE CROONIAN LECTURES ON THE 
 
 nervous tissue can be obtained by the discovery of certain pro- 
 ducts in the cerebrospinal fluid and blood of the patients. Of 
 these products choline, which can be readily identified by 
 chemical and physiological tests, was the one to which we par- 
 ticularly directed our attention; We now show that choline is 
 also discoverable in various diseases of the central and peripheral 
 nervous system, other than the one (General Paralysis) which 
 was the special subject of our earlier investigation. The evidence 
 on this branch of the question is described in the first part of the 
 present lecture. We have also directed our attention to the 
 micro-chemical reaction of Marchi, which is the histological test 
 most often resorted to for the detection of degenerated nerve- 
 fibres. We had noted that the same black colour is given by 
 ordinary fat, and it seemed possible that the explanation of the 
 Marchi reaction was that in the disintegration of lecithin, which 
 results in the liberation of choline, there is also a liberation of 
 the phosphorised portion of the molecule ; this would leave the 
 fatty portion of the molecule, which would give the Marchi 
 reaction. Preliminary experiments on human spinal cords, one 
 side of which showed degeneration, supported this view, for 
 the amount of phosphorised fat was much diminished on the 
 degenerated side. 
 
 Still, in order to place the matter on a satisfactory basis, it 
 appeared essential to undertake experiments on animals ; for in 
 these the steps of the process can be more accurately studied, 
 and the histological and chemical changes considered side by side 
 and correlated. The details of the experiments on cats to work 
 out this idea are given in the later part of this lecture, and the 
 results have fully confirmed our expectations. Wallerian de- 
 generation was produced in a series of eighteen cats by section of 
 both sciatic nerves ; the animals were killed at intervals of from 
 one day to one hundred and six days after the operation. 
 
 The nerves remained excitable up to the third day ; these 
 nerves were practically healthy both to the microscope and in 
 chemical composition ; the amount of water and of phosphorus 
 were the chemical data which were worked out. 
 
 Beyond the third day, early signs of degeneration set in ; the 
 amount of phosphorus in the nerves slightly dropped, and the 
 amount of choline in the blood slightly increased. 
 
 On the eighth day the Marchi reaction became strongly 
 
CHEMICAL SIDE OF NERVOUS ACTIVITY 97 
 
 marked. This date is coincident with a great drop in the 
 amount of phosphorus in the nerves, and with the appearance 
 of a large quantity of choline in the blood. 
 
 The Marchi reaction remained at its acme up to the thirteenth 
 day, and the amount of phosphorus became less and less. The 
 amount of choline became somewhat less in the blood ; it therefore 
 appears that of the disintegration products of lecithin the choline 
 is earliest removed, the phosphorus probably in the form of phos- 
 phoric acid next, leaving the fatty material to give the Marchi 
 reaction, and to be absorbed last. 
 
 By the twenty-seventh day all the phosphorus had nearly, 
 and by the twenty-ninth day entirely, disappeared. The removal 
 of the fat had also commenced, and we have drawn attention 
 to the phagocytic action of certain cells (in addition to leucocytes), 
 probably the multiplied neurilemmal cells in this process of fat 
 removal. 
 
 At the forty-fourth day the removal of the fat was all but 
 complete, and little remained except shrunken, empty nerve 
 tubules. But examination of the nerves sixty days after opera- 
 tion shows this date is variable with the vital reaction of different 
 animals ; at any rate in comparison with the central nervous 
 system the date is an early one. 
 
 Regeneration appears to begin about the same date. This is 
 about the sixtieth day in nerves which had united spontaneously, 
 though somewhat earlier in cases where the loose ends of the 
 nerves had been sutured together. 
 
 By the 100th to 106th day regeneration was well marked, 
 especially in sensory fibres, and the nerves were once more 
 excitable. By this date the fibres were seen to be fine and medul- 
 lated ; they took stains normally. Their chemical condition had 
 practically returned to the normal also. The first sign of the 
 return of the phosphorus was seen with the commencement of 
 myelinisation on the sixtieth, but it was well marked on the 106th 
 day. We found the percentage of phosphorus in normal nerves 
 to be 1-16. In the regenerated nerves it was 0-93. Whether all 
 the phosphorus in the regenerated fibres was in the medullary 
 sheath, or partly in the comparatively large axis cylinder, we 
 cannot say. 
 
 With regard to the amount of water in the nerves, the tables 
 of analyses we present show that the amount of water increases 
 7 
 
98 
 
 THE CKOONIAN LECTURES ON THE 
 
 with the degeneration, and continues high while absorption is 
 occurring. It sinks to the normal when regeneration has set in. 
 The following tabular summary gives our main results : 
 
 Days after 
 section 
 
 Cats' sciatic nerves 
 
 Condition of blood 
 
 Condition of nerves 
 
 Water 
 
 Solids 
 
 Percentage of 
 phosphorus 
 in solids 
 
 Normal . . 
 13 .. 
 
 46 .. 
 
 65-1 
 64-5 
 
 69-3 
 
 34-9 
 35-5 
 
 30-7 
 
 1-1 
 0-9 
 
 0-9 
 
 [Minimal traces 
 j of choline pre- 
 ( sent 
 Choline more 
 
 (Nerves irritable 
 j and histologi- 
 cally healthy 
 Irritability lost; 
 
 
 
 
 
 abundant 
 
 degeneration 
 
 
 
 
 
 
 beginning 
 
 8 
 10 
 13 
 
 68-2 
 70-7 
 71*3 
 
 31-8 
 29-3 
 28-7 
 
 0-5 
 0-3 
 0-2 
 
 1 Choline abun- 
 j dant 
 
 Dege neratioii 
 well shown by 
 Marchi reac- 
 tion 
 
 
 
 
 
 
 Marchi reaction 
 
 
 
 
 
 
 still seen, but 
 
 25-27.. 
 
 72-1 
 
 27-9 
 
 traces 
 
 f Choline much 
 
 - absorption of 
 
 29 
 
 72-5 
 
 27-5 
 
 o-o 
 
 } less 
 
 degenerated fat 
 
 
 
 
 
 
 has set in 
 
 44-60 . . 
 
 72-6 
 
 27-4 
 
 o-o 
 
 Choline almost 
 
 Absorption of 
 
 
 
 
 
 disappeared 
 
 fat practically 
 
 
 
 
 
 
 complete 
 
 100106 
 
 66-2 
 
 33-8 
 
 0-9 
 
 Choline almost 
 
 Return of func- 
 
 
 
 
 
 disappeared 
 
 tion ; nerves 
 
 
 
 
 
 
 regenerated 
 
 We have paid some attention to the multiplication of the cells 
 of the primitive sheath. This first becomes a marked phenome- 
 non on the eighth day, and is possibly the result of irritation 
 by the degenerated products. The phagocytic action of these 
 cells at a later stage has been already mentioned. Later still, 
 the cells become spindle-shaped and united end to end ; it appears 
 to us that these cells are in their activity related nutritionally to 
 the regeneration process. We have discussed the question 
 whether or not they may take any part in the actual formation of 
 the new axis cylinder, but at present we have insufficient evidence 
 to show that they do so. 
 
 Another question, which has not been alluded to in the fore- 
 going pages, but which has inevitably been considered by us, is 
 the mode of origin of the medullary sheath. The activity of the 
 neurilemmal cells is a point in favour of the origin of the medul- 
 lary sheath from them. On the other hand, the association of 
 the complete return of function with the appearance of the 
 
CHEMICAL SIDE OF NEKVOUS ACTIVITY 99 
 
 medullary sheath, would rather be in favour of the other theory, 
 that it originates from the axis cylinder. This is supported by 
 the fact that in the central nervous system the primitive sheath is 
 absent. 
 
 The axis cylinder and its sheaths must necessarily, for descrip- 
 tive purposes, be considered separately. There is little doubt in 
 our own minds that, functionally, all three parts of a nerve-fibre 
 must be considered to act as an organic whole, with intimate 
 inter-relations of a nutritional or metabolic nature. 
 
 These, after all, are but side issues from our main point, 
 which has been the elucidation of the relations between the 
 histological and chemical characters of the degeneration process.