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 littp://www.arcliive.org/details/accountofreasoniOOmack 
 
AN ACCOUNT 
 
 OF 
 
 THE REASONING PROCESS, 
 
 LOUIS MACKALL, M. D. 
 
 "I EXPRESS MYSELF WITH CAUTION, LEST I SHOULD BE MISTAKEN TO VILIFY REASON J 
 WHICH IS, INDEED, THE ONLY FACULTY WE HAVE WHEREWITH TO JUDGE CONCEENINO 
 
 ANY THING." — Bufler's Analogy. 
 
 WASHINGTON: 
 
 GIDEON & CO., PRINTERS. 
 
 1850. 
 

 Entered according to Act of Congress, in the year 1850, by 
 
 LOUIS MACKALL, 
 
 In the Clerk's Office of the District Court of the District of Columbia. 
 
AN ACCOUNT OF THE REASONING PROCESS. 
 
 (1.) Every human being, in whatever condition he maybe placed, or in 
 whatever occupation or pursuit he may be engaged, is constantly urged to 
 the exercise of Reason, for the purpose of finding out rules of conduct, or 
 the laws of nature relating to the subjects about which his thoughts are 
 employed. 
 
 (2.) This act, properly called the Reasoning Process, is a function of the 
 mind, as the circulation of the blood, digestion, &c., are functions of the 
 body, and is the characteristic that distinguishes the human mind from 
 that of brutes.* It is the means bestowed by the Author of nature on man, 
 by which he is enabled to acquire the knowledge that may be useful to 
 him for the various purposes of life. 
 
 (3.) Science, properly so called, is conversant only about rules or laws 
 and may be separated into two grand divisions. The one including the 
 Physical or Natural Sciences, which relate to the laws of nature, or 
 the laws which, in all the changes constantly taking place in the world 
 around us, are invariably observed. The other division, comprehending all 
 other sciences. 
 
 (4.) In the former division, the rules or laws are fixed and established 
 by the Creator. To these there are no exceptions. A single clear and 
 unequivocal exception to any proposition assumed to be a law of nature, is 
 a complete refutation of such proposition. 
 
 In the latter division of the sciences, rules or laws may be laid down as 
 the result of generalization, to which many exceptions may be found, with- 
 outat all invalidating these rules. 
 
 (5.) The functions of the body — digestion, the circulation of the blood, 
 &c., are performed by means of several organs. To understand the nor- 
 
 * This remark requires some qualification. There are two distinct modes of reasoning. 
 . In the one, laws are traced out so that they may be expressed in words, or recorded in 
 writing; to knowledge thus acquired I propose to Hmit the term Science. It is this kind 
 of reasoning that is characteristic of the human intellect. But there is an imperfect kind 
 of reasoning wherein a knowledge of laws is attained, vague, it is true, and indistinct, yet 
 sufficiently defined to influence actions. To knowledge arrived at in this way, we think 
 it advisable to confine the term Experience. Brutes seem to be capable of this mode of 
 reasoning to a certain extent. 
 
mal state of these functions, or to correct the derangement of them, 
 it is necessary to attend to the action of the organs concerned in such 
 functions. The mental function or Process of Reasoning, is, in like man- 
 ner, the result of the exercise of several of the organs or faculties of the 
 mind; and to correct the defects or faults to which it is hable, it is equally- 
 necessary to look to the exercise of these faculties. A true account, then, 
 pointing out the particular faculties engaged in this process, must be a 
 subject of the greatest interest. 
 
 (6.) In every legitimate act of Reasoning, there must be the exercise 
 of three of the faculties of the mind— Observation, Imagination, and Judg- 
 ment — and the exercise of these faculties must take place in the order in 
 which they are here enumerated. 
 
 The province of Observation is the notice or apprehension, as logicians 
 say, of particulars or instances. The exercise of the Imagination consists 
 in casting about, as it were, for the purpose of finding some proposition 
 or hypothesis, that may be applicable to the instance observed. The 
 Judgment is then called on to decide, if the proposition found by the 
 Imagination be applicable to the particular instance ; if all the circum- 
 stances attending be fully and satisfactorily explained ; and, finally, it 
 must appear to the Judgment that the hypothesis is applicable in like 
 manner to other similar instances. 
 
 (7.) The distinction I have made, among the objects of science, will be 
 found to be of great practical importance, and must be constantly borne in 
 mind, if we would avoid confusion of thought, or the most erroneous con- 
 clusions. From a neglect of this precaution, many rules or laws have been 
 admitted into the physical sciences, having no general application, and 
 consequently leading to conclusions, palpably erroneous or ridiculously ab- 
 surd. In the other sciences, a neglect of this same precaution gives rise to 
 all the baneful effects resulting from Fanaticism. In politics, ethics, <^c., 
 wherein exceptions to the rules or laws which constitute the science, are 
 not only allowable but must be admitted, the Fanatic madly insists on giv- 
 ing such rules or laws, the force and authority of laws of nature. He will 
 listen to nothing that appears to be an exception to his rules. 
 
 (8.) The plain and simple account, given above, of the Process of Rea- 
 soning, I will presently endeavor to illustrate, by shewing its operation in 
 the discovery of a law of nature. We will first, however, point out what 
 appear to us to be the defects in the accounts of this process, which have 
 been given by others. 
 
 (9.) Two systems or methods of Reasoning have been proposed. One 
 by Aristotle, called the Aristotelian or Syllogistic method ; the other by 
 Lord Bacon, called the Baconian or Inductive method. What appears to 
 
us to be very remarkable about these systems is, that although each of 
 their authors professed to give an account of the same process, and al- 
 though these two accounts differ from one another in toto, yet it is gene- 
 rally admitted, that they do not clash with, or contradict each other. 
 " Bacon's Organon," it is said, " is not intended to supersede that of 
 Aristotle." 
 
 The only way that occurs to us, by which this apparent contradiction 
 can be explained, or this discrepancy reconciled, is to suppose that which, 
 in my opinion, is true, viz., that each of these writers gave an account of 
 a part only, and that each selected a different and distinct part, of the pro- 
 cess; the Syllogistic method having reference only to what we have stated 
 to be the third part, that in which the Judgment is concerned ; the In- 
 ductive method having reference only to the first part, wherein Obser- 
 vation is exercised. 
 
 (10.) It is generally objected to the Syllogistic method, that it is use- 
 less as a means of discovering new truths. One of the ablest advocates 
 of this system, of the present day, in endeavoring to do away the force of 
 this objection, is compelled to take the strange position that Reasoning is 
 not intended as a means of discovering any new truth, but that its object is 
 '^ merely to expand and unfold the assertions wrapt up, as it were, and 
 implied in those with which we set out, and to bring a person to perceive 
 and acknowledge the full force of that which he has admitted ; to contem- 
 plate it in various points of view, to admit in one shape what he has 
 already admitted in another, and to give up and disallow whatever is in- 
 consistent with it." 
 
 (11.) The view thus taken by Bishop Whately of the object of rea- 
 soning, and the admission, that the Syllogistic method accomplishes merely 
 this object, confirm the opinion I have expressed that it relates only to the 
 latter part of the process ; for, it is evident, that what he has repre- 
 sented to be the whole process, should properly be regarded as the work 
 of the Judgment alone. 
 
 (12.) What it was that Lord Bacon intended when he proposed the In- 
 ductive method, or what particular method he had in view, it is not easy 
 to say. He has not only failed to give an intelligible account of it, but he 
 seems, in his writings, studiously to avoid leaving any trace or clue by 
 which his meaning could be ascertained. He gives us to understand, 
 indeed, that he had discovered a rule, by means of which, any person, of 
 ordinary powers of intellect, could, with certainty and in a short space of 
 time, find out a new scientific truth, which could not be arrived at without 
 the use of this rule; at least not without hard and laborious study, and that 
 continued for a length of time. Yet neither he, nor any one since his time. 
 
has, by means of any rule laid down by him, or which could fairly be in- 
 ferred from his writings, discovered any such truth. 
 
 (13.) The author of this system, in the course of his work, deludes us 
 with the promise of giving an example* that might make his meaning, in 
 relation to his rule, understood; but breaks off in the middle of the exam- 
 ple, without having come to any conclusion whatever; and tells us that he 
 does this lest his rule may be disclosed, which, for the present at least, he 
 intends to keep a secret. This secret has never yet been divulged. That a 
 system, such as this, should have enchained the attention of men of learn- 
 ing, throughout the seventeenth, eighteenth, and half of the nineteenth 
 century, would appear to be one of the most remarkable phenomena to be 
 observed in the history of the human mind, during that time. 
 
 (14.) The explanation of this phenomenon is to be sought in various 
 circumstances, one of which is well presented by Bishop Whately, in a 
 remark which he applied to a different subject: "I am convinced, says he, 
 that a verbose, mystical, and partially obscure Way of writing on such a 
 subject, is the most likely to catch the attention of the multitude. The 
 generality verify the observation of Tacitus: "Omne ignotum, pro mirifi- 
 co." Another circumstance is, that the author professed to write in such 
 a manner as to select his readers, and to exclude those who were incom- 
 
 * " Let the effect to be produced be whiteness ; let the first direction be, that if air and 
 water be intermingled, or broken in small portion together, whiteness will ensue ; as in 
 snow, in the breaking of the waves of the sea and rivers, and the like. This direction is 
 certain but very particular, and restrained, being tied but to air and water. Let the second 
 direction be, that if the air be mingled, as before, with any transparent body, such never- 
 theless as is uncolored, and more grossly transparent than air itself, that then, &c., as 
 glass or crystal being beaten to fine powder, by the interposition of air becometh white; 
 the white of an egg being clear in itself, receiving air by agitation becometh white, receiv- 
 ing air by concoction becometh white ; here you are freed from water and advanced to a 
 clear body, and still tied to air. Let the third direction exclude or remove the restraint of 
 an uncolored body, as in amber, sapphires, &c. , which, beaten to fine powder become, white 
 wine and beer; which brought to froth become white. Let the fourth direction exclude 
 the restraint of a body more grossly transparent than air, as in flame, being a body com- 
 pounded between air and a finer substance than air ; which flame, if it were not for the 
 smoke, which is the third substance that incorporateth itself and dieth, the flame would 
 be more perfect white. In all these four directions air still beareth a part. Let the fifth 
 direction then be, that if any bodies, both transparent but in an unequal degree, be mingled 
 as before, whiteness will follow ; as oil or water beaten to an ointment, though by settling 
 the air which gathereth in the agitation be evaporate, yet remainelh white, though not so 
 perfect. Now are you freed from air, but still you are tied to transparent bodies. To 
 ascend farther by scale I do forbear, partly because it would draw on the example to an 
 over-gi-eat length, but chiefly because it would disclose that which in this woik I deter- 
 mine to reserve." — Bacon's Interpretation of Jfature, ch. 12. 
 
petent to judge of his undertaking. Every one preferring to embrace 
 the system, right or wrong, rather than incur the imputation of being 
 incompetent to understand it. But the principal circumstance in which 
 the explanation of this phenomenon is to be found is, that this Baconian 
 system really contained a most important truth; this truth, although occu- 
 pying a subordinate position in the system, and, although it was regarded 
 by its author as of secondary consideration, yet was the main support that 
 has sustained it so long. 
 
 (15.) Lord Bacon, in proposing this inductive method, constantly points 
 out, and forcibly presents to the mind, the necessity of attending to par- 
 ticulars. The truth is everywhere inculcated by him that the observation of 
 particulars or instances, is a necessary preliminary in any attempt at the 
 invention of new truths. This had not been attended to, before his time. 
 Imagination had been allowed frequently to usurp the place of obser- 
 vation, and this, very naturally, lead to a habit of reasoning, which ended 
 only, as he expresses it, in "monstrous altercations, or barking questions. " 
 
 (16.) The Baconian system was calculated to give a better direction to 
 the human mind in its efforts at reasoning. Its author, however, seems 
 to have had but a vague and indefinite notion of this process. He was 
 not aware that the exercise of the imagination was an essential step in it; 
 but, on the contrary, he seizes every occasion to vilify and traduce this 
 faculty, and regards it as the one with which philosophers should have 
 nothing to do. The great merit of this system consists in its having di- 
 rected attention to the importance of exercising the observation, in every 
 act of reasoning, or, in other words, to the importance of starting out from 
 positive facts, whether originally observed, or taken from books, or from 
 the observation of others. 
 
 (17.) That the estimate we have now made of the Baconian philosophy 
 is just, maybe shown by a glance at the present condition of the Sciences, 
 which condition is fairly attributable to the influence of this philosophy. 
 The votaries of science, in modern times, are intent only on the observa- 
 tion of particulars, or, as they express it, "on the acquisition of facts." If 
 you converse with a man of science (I speak of the generality of those 
 professing to be such) on any scientific subject, and should happen to make 
 an allusion to a law of nature, he immediately regards you with suspicion; 
 but if you should, unfortunately, state a theory, or an hypothesis, he sets 
 you down at once as a visionary speculatist, or something worse, and 
 will tell you, with much self-complacency, that he never theorizes — he 
 is concerned only about facts, and is governed solely by experience. He 
 holds theories and hypotheses in utter contempt; for it has never occurred 
 to him that by these, all our knowledge must be acquired. 
 
(18.) The modern astronomer proposes to himself, as the object of his 
 ambition, the discovery of some distant planet, that has heretofore escaped 
 observation; the anatomist seeks diligently for some stray muscular fibres, 
 that have eluded the vigilance of his predecessors, which he may dignify 
 with the name of muscle, and to which he may attach his own name; the 
 zoologist searches for some animal that has never been described; and the 
 botanist wearies himself in looking for some rare plant which . has not 
 found a place in any herbarium. 
 
 (19.) If any of these attain the object of their ambition, they are con- 
 sidered as having borne off the palm ; they are thought to have accom- 
 plished the highest purpose for which the human intellect was designed. 
 They are lauded for enlarging the boundaries of science, and in thus being 
 the benefactors of the human race. Their names ate handed down to 
 posterity, and become immortalized. 
 
 But, to return to our promise to illustrate our view of the Reasoning Pro- 
 cess, by showing its operation in discovering a law of nature. For this 
 purpose we will choose one which we have ourselves traced out by this 
 means. 
 
 (20.) The first part of the process of Reasoning, I have said, consists in 
 the observation of particulars or instances. The instance I shall select on 
 this occasion is related by naturalists, and is well calculated to arrest 
 attention. I allude to the protrusion of the tongue of the chameleon, 
 when this animal is engaged in seizing its prey. The tongue, when in a 
 quiescent state, or when fully retracted, is about an inch in length. When 
 observed in this state, the end, or what is called the bulbous part, only is 
 visible ; but what is remarkable about it is, that the extremity, like that of 
 the trunk of the elephant, is formed into the shape of, and used as a pair 
 of, forceps. The animal, we are told, when about to catch its prey (com- 
 monly a fly or some small insect) directs its mouth towards the object, 
 taking aim, as it were; and when within about eight inches, opens its 
 mouth, and suddenly, and with the celerity of lightning, protrudes its tongue, 
 seizes its prey with the forceps of which we have spoken, and then more 
 leisurely draws it into its mouth. 
 
 (21.) The anatomical structure of the tongue and of the parts to which 
 it is attached, is shown in the annexed plate. No. I, taken from the illustrated 
 catalogue of the Hunterian Museum, vol. iii, pi. xxx. The os hyoides (c) 
 is represented, extending with its rami, as in other animals, from one side 
 of the throat or neck to the other, in the form of a bow. From the mid- 
 dle point of this, another bone, the os linguale (d) projects anteriorly; and 
 upon this the tongue is drawn when retracted, like the finger of the glove 
 upon the finger. The central structure of the tongue (/) is composed of a 
 
series of fibrous bands, like hoops, extending from one extremity to the 
 other, having their exterior margins connected together by loose cellular 
 tissue, and thus the organ is well adapted for its retraction upon the 
 OS linguale. The structure now pointed out may be aptly compared to 
 the bag of a partridge net — the fibrous bands to the hoops, and the 
 cellular tissue to the net which passes over the hoops and connects 
 them together. Two largely developed muscles (A) arise, one from 
 each ramus of the os hyoides, and passing on each side of the cen- 
 tral structure, are finally distributed to the bulbous part or extremity 
 (§•.) A large nerve (i) accompanies each muscle to supply it with nervous 
 influence, and by its wavy or zigzag course, well reminds us of the fact 
 that this tissue is inelastic, and consequently that all organs or members 
 of an animal capable of sudden or speedy extension, must have a length 
 of nerve corresponding to their capability of extension. 
 
 (22.) When we contemplate the protrusion of this organ, we instinctively 
 ask the question, how is this remarkable phenomenon to be explained? 
 The observation of similar instances, or of any number of instances, it is 
 clear, could never furnish an explanation. Something else must be done; 
 a law of nature must be found to which it may be referred, before we can 
 satisfy this inquiry. Here, then, we come to what I have called the se- 
 cond part of the process of Reasoning. This is to call into exercise the 
 imagination, or what Lord Bacon called the anticipation of the mind, in 
 order to form a conjecture or hypothesis that may explam this phenome- 
 non. 
 
 (23.) To what law of nature is this extension of the tongue of the cha- 
 meleon to be referred? Mr. John Hunter taxed his imagination to find out 
 a law that should answer this purpose. Let him have the benefit of his 
 own words: "The first of these (the fibrous rings or hoops) appears to be 
 composed of rings, or something similar, placed obliquely in contrary direc- 
 tions, so as to appear to be two spirals crossing one another. Whether the 
 other or softer substance, (the loose cellular tissue connecting the hoops) 
 has any direction of fibres I could not observe, but I suspect it is muscular. 
 If I am right in my conjecture of this structure, and of its disposition, it 
 wiU be nOj difiicult thing to show how it may be elongated; for, if these 
 rings are placed transverse, they may be brought so near to one another 
 as to shorten the whole very considerably; and if they allow of being 
 placed almost longitudinally, they must of course lengthen it very consid- 
 erably, and this position can be easily produced by muscles, which I take 
 the pulpy substance to be." 
 
 (24.) The absurdity of this explanation is so manifest, that it would be 
 a waste of time to point it out in detail. Its author, to construct his hy- 
 2 
 
10 
 
 pothesis at all, was compelled, by an eiFort of his imagination, to convert 
 loose cellular tissue into muscles, and to invest the fibrous rings with pro- 
 perties and powers which they could not possess. This hypothesis, how- 
 ever, such as it is, was the- result of the exercise of Mr. Hunter's imagi- 
 nation. 
 
 (25.) Mr. Houston, another writer on this subject, in the transactions 
 of the Irish academy, rejected Mr. Hunter's explanation as being chime- 
 rical, and offered one in its place. He observed two large sized arteries, 
 passing one to each of the lingual muscles, supplying it with blood; and he 
 imagined that the protrusion of the tongue was eifected by the injection of 
 these two arteries. This hypothesis, it is true, was not new. Physiologists 
 had applied it for a long time to explain the action of many organs which 
 they imagined to be endowed with a peculiar structure, called the erectile 
 tissue; but this was perhaps the first time it had been applied to the ex- 
 planation of this particular instance. 
 
 (26.) I shall take some future occasion to show the fallacy of this hy- 
 pothesis whenever applied. It will be a sufficient refutation of it, however, 
 in the present instance, to advert to the fact, that it is utterly impossible 
 to conceive that the blood could be transmitted through its vessels with 
 the velocity necessary to account for the suddenness and celerity with 
 which the organ is said to be elongated. 
 
 Having pointed out what I consider objections to the two hypotheses 
 advanced to explain this phenom.enon, (and I believe these are all that 
 have been formed,) I proceed to propose a substitute for them. 
 
 (27.) In casting about for a proposition, we gain a useful direction by 
 referring to what is already known. It is a law of nature, known to phy- 
 siologists, that all voluntary motion is effected by means of muscles, or of 
 muscular fibres. This protrusion of the tongue of the chameleon being a 
 voluntary motion, we must necessarily look to the muscles of the organ 
 as being the instruments by which it is effected. There are but two mus- 
 cles that could be concerned in this act; and these, (the lingual muscles,) 
 from their being largely developed, and from their being so liberally sup- 
 plied with both nerves and blood-vessels, would seem, indeed, well adapted 
 to such a purpose. But we are met here by a difficulty: it is assumed by 
 physiologists to be a law of nature, that muscular action consists in con- 
 traction. If this assumption be admitted to be true, the difficulty, we must 
 confess, is insuperable. But whoever has carefully reflected upon the 
 present condition of physiological science, knows, that what is therein ad- 
 mitted is not necessarily true; and they who have traced its history are 
 well aware that the grossest errors have not only been admitted into that 
 science, but that they have frequently remained there, without being called 
 
11 
 
 down, for centuries. The assumption that causes the difficulty, in the 
 present instance, may be an error of this kind. 
 
 (28.) If this difficulty be put aside, and if, contrary to the assumption, 
 that muscular action consists in contraction, we assume it to be a law of 
 nature, that the action of a muscle consists in the active elongation or ex- 
 tension of its fibres, the explanation of the phenomenon we are considering 
 will be easy. The animal determines the nervous fluid, which is admitted 
 to be the cause of muscular action, to the lingual muscles, through the 
 large nerves which accompany them — these muscles thus become actively 
 elongated, and the tongue is protruded to the extent and with the celerity 
 which have been noticed. This, then, is the proposition we have found 
 by the exercise of the imagination, viz., that muscular action consists in 
 active elongation or extension. 
 
 (29.) The contraction of muscles may readily be explained in accord- 
 ance with this law. If an animal possesses the power of determining its 
 nervous fluid in one direction, it may determine it in another. If its de- 
 termination to a muscle, causes its elongation, a determination from the 
 muscle, either by withdrawing it to the nervous centre, or diverting it into 
 some other channel, would cause its contraction. 
 
 (30.) Having found a proposition or hypothesis applicable to the in- 
 stance before us, the work of the imagination is done. That which we 
 have represented to be the second part in the process of Reasoning, is 
 completed, and the third and last part only remains to be attended to. The 
 judgment, we have said, must be called into exercise to decide, if the 
 proposition, found be fairly applicable to the instance in hand, and if aU 
 the material circumstances connected with it be fully and satisfactorily 
 explained. The hypothesis I have proj)osed, is simple, and, I think it will 
 be admitted, fulfils these requirements; whilst those advanced by Mr. 
 Hunter and Mr. Houston are objectionable, not only in not explaining the 
 circumstances, but in being far-fetched and unnatural. 
 
 (31.) But it must also appear to the judgment that the proposition, if 
 assumed to be a rule, must be applicable to other similar instances; or, if 
 assumed to be a law of nature, to all similar instances. I will proceed to 
 apply this test also to the law proposed. There will be no difficulty in 
 finding instances for this purpose; they are to be met with in every page 
 of physiology, both human and comparative; but not to weary the atten- 
 tion I will select two only, to give in detail. 
 
 (32.) Dr. Arthur Farre, in the second part of the Philosophical Trans- 
 actions for 1837, has given a very interesting description of certain small 
 aquatic animals, which he called Bryooza. These animals are composed 
 
12 
 
 externally of a horny tube or cylinder, open at top; the interior consists^ 
 mainly, of its organs of digestion and their appendages. The latter, termed 
 tentacula, are capable of being protruded from the extremity of the horny 
 tube for the purpose of collecting particles of food, or nourishment, from 
 the surrounding medium. Placed at regular intervals around, and conve- 
 niently inserted into the tentacula, are muscles or bundles of longitudinal 
 muscular fibres, which arise from the inner and upper surface of the exter- 
 nal cylinder. 
 
 (33.) The protrusion of the tentacula is what we are at present inter- 
 ested in; and it is curious to notice the hypothesis which Dr. Farre 
 formed to explain it. He observed the muscles of which we have just 
 spoken; that they were well developed, an^ thought them admirably 
 adapted to the retraction of the organs; but was greatly puzzled, at first, 
 on finding no provision made, by nature, for the protrusion of them. 
 This must, indeed, have appeared to him singular, inasmuch as the 
 protrusion of the tentacula w^as confessedly of as much importance in 
 the economy of the animal as their retraction, for which such ample pro- 
 vision had been made. After closely examining a number of specimens, 
 however, he finally detected some few minute fibres running transversely 
 around the stomach of some of them. This fortunate discovery removed 
 all difficulty; the transverse fibres, he thought, when contracted, would 
 necessarily force out the fluid contents of the stomach, and along with 
 them the tentacula!!! It seems strange that such a hypothesis should ever 
 have been seriously entertained; but it is still more strange that another 
 writer, of high standing in his department of science, should have at- 
 tempted to apply it to other instances.* 
 
 (34.) On viewing the annexed plate. No. II, taken from Jones's Animal 
 Kingdom, p. Ill, representing the tentacula of Bryozoa in different stages 
 of extension, I think it will at once be understood how the law we have 
 proposed would furnish a satisfactory explanation of the protrusion of 
 these organs. The active elongation of the muscular fibres attached to 
 the tentacula would explain every thing. We wiU apply this law to an- 
 other instance. 
 
 (35.) The eyes of the snail, it is well known, are situated at the extre- 
 mity of two soft cylinders, or fleshy tubes, commonly, though improperly, 
 called its horns. Two well defined muscles, separate from the common 
 mass of muscle, by which the voluntary motions of the animal are effect- 
 ed, and passing through the abdominal cavity and that of the fleshy tubes, 
 are inserted immediately around the posterior border of the eyes. 
 
 * Jones's Animal Kingdom, p. 44, § 61- 
 
13 
 
 (36.) The best representation I have met with of the anatomy of this 
 organ, was found in the annexed plate, No. Ill, taken from the work last 
 quoted, p. 402. The muscles of the eyes (g) are there well shown, ac- 
 companied each by a large nerve, (/, h, ) which possesses the peculiarity 
 remarked when describing those of the tongue of the chameleon — that is, 
 a length adapted to the extent to which the muscle is capable of being 
 elongated. About the walls of the fleshy tubes, minute muscles, or bun- 
 dles of muscular fibres, are seen to be arranged circularly, (e.) 
 
 (37.) If we look at the plate representing this anatomy, we may readily 
 perceive how the animal, by determining the nervous fluid to the muscle, 
 and thus actively elongating it, could protrude the eye; and by ceasing 
 such determination, or by withdrawing the fluid, could shorten or contract 
 the muscle, and thus retract ike eye. We may farther understand, that 
 by calling into action, or elongating, the muscles or fibres about the walls 
 of the tubes, they might be dilated, for the purpose of affording free play 
 to the muscles and nerves passing through them. That such is the pur- 
 pose for which these muscles were designed we may be convinced, on 
 placing a living snail, when the eye is in full operation, between the light 
 and our eye; when we may see the tube dilated, and the muscle going to 
 the eye, extended, and plainly lying along the floor, as it were, of the 
 tube, but in contact with it only on one of its sides. 
 
 (38.) But what hypothesis does Mr. Jones adopt to explain this subject? 
 It is this: "To evert the tentacle (the horn of the snail) the contraction of 
 the circular muscles that form its walls is sufficient, as they can gradually 
 unrol the whole, by squeezing out, as it were, the inner portion; but to effect 
 its inversion a special retractor muscle is required! !!^^ 
 
 (39) A more extensive application of the law of nature, we have sug- 
 gested, is not consistent with the design of this paper. Any one, by turn- 
 ing over the leaves in a work on comparative anatomy, may find many 
 instances as strikingly illustrative of its truth as those we have given, 
 with explanations, too, as puerile and ridiculous. We may say, however, 
 in this connection, that we have, for more than sixteen years, carefully 
 observed or considered the operation of this law, in every form of muscle, 
 not only in the human subject, but also in all the lower orders, or ani- 
 mals, and that we feel fully justified in asserting that no exception to it 
 can be found. This, we consider, the only true test by which to know 
 if any proposition be a law of nature, and to this test we are willing to 
 submit our hypothesis. 
 
 (40.) We have thus given what we believe to be a true account of the 
 process of Reasoning, and shown its application in discovering a law of 
 nature. Happily, however, for mankind, we are not solely dependent. 
 
14 
 
 in our ordinary occupations, or in the common occasions of life, on the 
 rules or laws that have been fairly traced out, or clearly established and 
 laid down in words. So far as this has been done in relation to any sub- 
 ject, thus far is that subject reduced to a science; but reason is often 
 conducted tacitly, as it were, or secretly, and we arrive at conclusions 
 without being conscious that any such operation has taken place in the 
 mind; and what is very curious, the conclusions thus arrived at are, some- 
 times, not recognised when presented in words, or may even be unhesi- 
 tatingly rejected. That this secret process does take place, however, may 
 be inferred from the fact, that a knowledge of many of the laws of nature, 
 not otherwise known to them, is fairly implied in the conduct of indivi- 
 duals. 
 
 (41.) Innumerable instances might be adduced in confirmation of the 
 truth of this remark, but I will only mention two of them. A knowledge 
 of the law of nature, I have pointed out, is clearly implied in the daily 
 conduct of physicians. Not to mention other instances — when a muscle 
 becomes contracted by spasm or otherwise, friction, or other means of de- 
 termining the nervous fluid to the muscle, for the purpose, evidently, of 
 elongating its fibres to the normal state, is constantly resorted to. And, 
 on the other hand, when a blood vessel has its calibre increased by the 
 elongation of the fibres about its walls, (in consequence of the determina- 
 tion of the nervous fluid to those fibres,) as in active inflammation, the 
 physician invariably makes use of every means in his power to lessen that 
 determination of the fluid, by what is called the antiphlogistic regimen, or 
 to withdraw it or divert it into some other direction by means of revul- 
 sives. Again: 
 
 (42.) Although it has been known to some men of science, and has 
 even been formally laid down in the books, "that a law of nature has no 
 exceptions," yet the generality have paid no attention to this truth, nor 
 have they, knowingly, applied it to any practical purpose. It is to them, 
 then, as if it had never been known. When I have presented to such 
 persons, as I frequently have done, the law, "that muscular action con- 
 sists in active elongation," they instantly reject it, because they readily 
 find — what appears to them to be — exceptions to it. When we bend our 
 arm, say they, do we not know that the flexor muscles are in action; and 
 are they not contracted? When a muscle is pricked or pinched, is it not 
 stimulated into action, and is it not contracted? "So they turn away in a 
 rage." They do not stop to reflect, that in the former instance, by an 
 effort of the will, the nervous fluid may have been withdrawn from the flexor 
 muscles, and then their contraction be a passive state; and in the latter in- 
 stance, that the violent impression made upon the muscle may have ex- 
 
15 
 
 cited into action its corresponding nervous centre, and thus the nervous 
 fluid, or cause of action, may have been determined from the muscle to- 
 wards the centre, instead oi from the centre to the muscle. Nor do they 
 stop to consider, that it is more rational to attribute the contraction of 
 muscles to a withdrawal from them, than to a determination to them of the 
 nervous fluid. 
 
 (43.) A facility in carrying on this secret process of reasoning, is what 
 should be understood by the expression common sense. Any one posses- 
 sing common sense, and using moderate application, who is conversant 
 about any particular subject, soon acquires a knowledge of many rules or 
 laws relating to that subject, which are not contained in the books, or which 
 he could not otherwise arrive at. Yet, such person might not be able to 
 state, in words, a single law or rule that he had so acquired; nay, he might 
 even reject them if they were so stated. We may place confidence in a 
 physician known to possess common sense, and who has had much experi- 
 ence in his profession, notwithstanding we may be certain that he is not 
 aware of, or would reject if presented to him, what we know to be impor- 
 tant fundamental principles in the science of medicine. This secret rea- 
 soning, or the act of inferring or deducing rules or laws secretly, from facts 
 relating to subjects with which we are familiar, would be a very appropri- 
 ate meaning to attach to the word experience; that is, a finding out laws or 
 rules; and one who passes through life, and from indolence or incompeten- 
 cy, should fail to deduce laws from the facts connected with such subjects, 
 might with propriety be said, "to have grown grey without the benefit of 
 experience." 
 
 (44.) A reference to the process of which we are speaking, explains the 
 origin of the opinion of one of the ancient philosophers, "that all know- 
 ledge is but remembrance," and explains too, how it is, that in some in- 
 stances, when a new truth is presented to our minds, we seem to have 
 known it already; we recognise it as an old acquaintance. 
 
 (45.) But, it may be asked, if we can thus unconsciously reason out 
 rules or laws sufficient to direct us in our conduct, where is the advantage 
 of tracing them out with so much study and labor? What advantao-e has 
 science over experience? The advantages of science are infinite. We 
 can, by means of this alone, communicate our knowledge to one another. 
 The knowledge that is acquired unconsciously, is appHed for the most part 
 partially, or to but few particulars. That that is traced out and recorded, 
 gives to the mind freedom and liberty, as it were, to apply it to any num- 
 ber of instances. The former kind of knowledge enables us, indeed, to 
 grope our way so as to arrive at many desirable results; but the light it af- 
 fords is dim and flickering, and the mind ever remains vacillating and in 
 
16 
 
 doubt; but a knowledge of rules and laws, fairly traced out and firmly es- 
 tablished, removes all uncertainty, and places the mind in a state which is 
 truly represented in the following quotation: "It is a view of delight, to 
 stand or walk upon the shore side, and to see a ship tossed with tem- 
 pest upon the sea; or to be in a fortified tower, and to see two battles join 
 upon a plane; but it is a pleasure incomparable, for the mind of man to be 
 settled, landed, and fortified in the certainty of truth, and from thence to 
 to descry and behold the errors, perturbations, labors, and wanderings up 
 and down of other men." 
 
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