ea ahead: 5 My tdaigtr toh a) it - Ea LCA + a ny cev fyi hha! Teds ey at ctgtte , i cat Seah aa LIBRARY NEW YORK STATE VETERINARY COLLEGE ITHACA, N.Y. This Volume is the Gift of Dr. S. Weissman ine SPavin group of lameness DATE DUE The Spayin Group of Lamenesses W. L. WILLIAMS, Ithaca, N. Y., CARL W. FISHER, San Mateo, California, and D. H. UDALL, Ohio State University LIBRARY NEW YORK STATE VETERINARY COLLEGE ITHACA, N.Y. This Volume is the Gift of Dr. S. Weissman DATE DUE GAYLORD PRINTED INU.S.As : (TT TTT es The Spavin Group of Lamenesses W. L. WILLIAMS, Ithaca, N. Y.. CARL W. FISHER, San Mateo, California, and D. H. UDALL, Ohio State University Reprinted from 42d Annual Proceedings of A.V. M.A. HARTFORD, CONN. Press of the Case, Lockwood & Brainard Company 1906 The Spavin Group of Lamenesses. W. L. Wittiams, Irwaca,'N. Y., Cart W. Fisuer, SAN Mateo, CALI- FORNIA, AND D, H. Upati, Onto State University. Historically, spavin is perhaps the oldest lameness of the horse. Standing in the foremost rank economically, it has received at least as much, if not more study than any other. ‘Grouped about this malady and certainly allied, if not identical, to it, in cause and pathology, is a long'list of separately de- scribed affections, some of which may well challenge the suprem- acy of spavin itself in their frequency and power of diminishing or destroying the usefulness of the horse. We have, therefore, elected to give spavin the title réle, rather from convenience than from an inherent right of this one affection to dominate the nomenclature of this extensive group. Among the most com- mon and important members of the group, in their approximate order of frequency and economic importance, we would mention spavin, navicular disease, ringbone, sidebone, sesamoiditis, spinitis, gonitis, carpitis, humero-radial arthritis, scapulo-humeral arthritis, etc. In the observations of Dr. Fisher spavin should occupy third or fourth place in frequency. * Taken as'a group, they constitute by far the most important lamenesses and, in the destruction of the value of the horse, take high rank among all diseases to which this animal is liable. Under the title of arthritis sicca or arthritis deformans, numerous writers on general veterinary pathology group these affections together without definitely assigning them to a com- mon cause or suggesting, as a rule, any close relationship beyond the evident similarity of tissue changes, indeed most writers on regional surgery ignore generic identity and treat each as an isolated disease. Without desiring to detract in the. least. from the excellency of the very extensive literature upon these as separate diseases, we desire to present the entire category as one group of closely allied affections, or, rather, as a malady expressing itself by common phenomena in various parts of the skeletal tissues and in other parts of the integument. The senior author first had his attention attracted to the group, as such, through observations made as a result of a Williams, Fisher, and Udall: The Spavin Group. professional residence of some duration in the Rocky Moun- tains, the Mississippi Valley, and in the eastern United States extending altogether over a quarter of a century, in which it was seen that the malady, almost unknown in one region, became a scourge in another part of the country, and between the two extremes offered every possible variation; peculiarities which called for some deeper and more satisfying explanation than accident or traumatism. Later he enlisted the collaboration of C. W. Fisher, D. V. M., of San Mateo, California, and Professor D. H. Udall, D. V.M., of the Veterinary Department of the Ohio State University, - who selected this topic for their joint thesis for graduation at the New York State Veterinary College, and who, during the years from 1899 to 1901, conducted a series of original and highly instructive investigations in relation to its pathology, in which work they were ably advised by Dr. V. A. Moore. Since the presentation of their thesis, Drs. Fisher and Udall have had opportunities for further valuable observations. The wide geographical separation of the contributors permits the presentation of views based upon data obtained in numerous locations reaching across the continent from the Atlantic to the Pacific, and the subject to be viewed from the standpoint of student, practitioner, and teacher. The conclusions submitted constitute in general the joint views of the three authors. The major part of the thesis of Drs. Fisher and Udall is presented as such without essential change, for which they assume full responsibility. The respon- sibility for other portions is accepted by the senior author. The very instructive, though all too few, urinalyses herein quoted are the work of Dr. George W. Cavanaugh, Professor of Agricultural Chemistry, Cornell University, the samples and clinical data having been supplied by the senior author. PATHOLOGY. This affection or group of affections having been generally viewed as the result of a traumatism, the pathology has been chiefly studied in the light of separate localized maladies, con- sequently each has had its morbid anatomy investigated and described separately, each description being a repetition of the other varying only in the predominance of this lesion in one, = Williams, Fisher, -and Udall: The Spavin Group. 5 of that in another. True, here and there an author has vaguely hinted at the systemic etiology of one or another member of the group, as has Dieckerhoff (Der Spat des Pferdes) in rec- ognizing brustseuche as an essential cause of some cases of spavin. During the period of our study and subsequent to the prep- aration of the thesis mentioned, Messrs. Vivien and Augustin, in the Revue Generale de Leclainche for July, 1904 (Am. Vet. Review, Nov., 1904, page 712), came forward with a thesis ascribing this group essentially to systemic disturbances and assigning to trauma a secondary rdle so that, working without knowledge of the trend of each other’s investigations, the gen- eral conclusions have proven parallel in some of their leading features. In dealing with the pathological anatomy, it is not essential for us to enter into it in detail, since the data published by any one of several authors would necessarily be repeated, and if included as related by any one of them regarding one of the group of maladies, would serve for a description of the lesions of any other one or all of them almost indifferently. Were we to take the descriptions of the lesions of spavin by Percivall, Dieckerhoff or Eberlein, they would, in a large measure, corre- spond, varying somewhat because of the bias of each as to the etiology of this affection, and if we set aside the influence of this belief, then each description would serve equally well for ringbone, navicular disease or other member of the group. If we select from the most extensive and recent investigations in the histology of these affections, we would mention Eberlein (Monatshefte fur Praktische Thierheilkunde, Vol. IX, pp. I-49) as to spavin, and Karnbach (Monatshefte fur Praktische Thier- heilkunde, Vol. XI, page 516), and Udriski (Ibid, page 337) on ringbones. The initial point of the disease process is variously held by different authors, in harmony with their views as to the cause. If the systemic hypothesis of Vivien and Augustin and that of ourselves be accepted, the pathologic orgin is general, and the controversy has been waged over the first region of visible intensity, which may vary in different cases. The disease, according to our observations, affects the entire skeletal system, involving primarily the ‘general system and causing constitu- tional disturbances, of which the arthritis becomes the local 6 Williams, Fisher, and Udall: The Spavin Group. manifestation. With such a view, it follows that no articular tissue occupies a first place in the history, but any one of the tissues concerned may be the first to become visibly affected. BoNE AND ARTICULAR CaRTILAGE. The short bones, composed of cancellated tissue and having an abundance of red marrow, take a prominent, if not the chief part in the known pathologic changes, and, according to many recent investigators, is the tissue in which the first visible lesions of the disease appear. These lesions are first discoverable chiefly in the subchondral layer, and may be seen by the naked eye in -early stages as variable sized, dark reddish-blue spots through the compara- tively transparent articulat cartilage, as is shown at I, 2, 4; 5, 6, 7 in Fig. I and at B in Figs. II and IIT. These areas are irregularly circular in form and tend to occur simultaneously at corresponding points on the ends of the two bones concurring in the articulation. ‘Histologically examined, the Haversian canals widen greatly, assuming sac-- or ampulla-like enlargements designated How- schip’s lacunee. The bone cells decrease in size, their prolonga- tions disappear and their outline becomes more regular. The canaliculi vanish in the severely affected parts. The bone matrix liquefies, forming cavities of considerable size, and, by exten- sion toward the articular cartilage, finally reaches it, and the granulation tissue interrupting the nutrition to the superposed cartilage, it, too, becomes involved. The disease of the cartilage generally begins in the deepest layers, bordering the subchon- dral excavations in the osseous tissue, the superficial cartilagi- nous layers remaining for a time intact. The disease processes within the cartilage are analogous to those taking place in the bone. The cartilage cells multiply, enlarge, lose their normal character, and assume the appearance of giant cells or osteo- clasts. The chondral matrix softens, becomes fibrillated and destroyed. When the superficial layer of cartilage is finally dissolved or thoroughly undermined by the erosive process tak- ing place in the subchondral bone, it breaks and falls into the excavation beneath, forming deep pit-like cavities, opening upon the articular surface by a mouth usually much smaller in diam- eter than the excavation beneath, producing the macroscopic ‘appearances shown in Figs. II IV. These pits appear to be always the seat of active inflam- mation, are occupied in part by tissue débris which has become Fic. 1.— Symmetrical sesamoiditis. A, Metacarpus; B, Suffraginis; C, Sesamoids. I. x, 2, 4, Erosions of articular cartilage, with darkened background. 3, Repaired fissure of the head of xst phalanx. II. 5, 5, Erosions apparently from friction. 6, 7, Erosions with dark background. 8, 8, Ex- ostoses on sesamoid bone. ‘yuawe3] repnsdeo paueyory3 A[snoursous ay Ul peppequit sliqep jo sesswur SN01ID9N ‘G ‘d= ‘sHqep oMor0au yy pey sud ay ‘sjyutof jo aouerayumnoio ye suoq pue aSy[niies Jo suotsorg ‘9 ‘D ‘avog jo see powleyur Yiep uodn Ajayerpeurw: Suyser sepysreo repnoiiy ‘gq ‘gq raSepied ae[nonie yewsou Ayeyeuxoiddy ‘y ‘y ‘348 ey] Je sniduny {yer ye eppdvog -‘wauroeds jam ulosj UMeIp ‘sIIYyIe TeauInY-ojndess —"]] “DIF Fic. III. — Longitudinal Section of humerus, shown in Fig. I. A. Approximately normal articular cartilage. . B. Darkened area in bone, due to intense inflammation, corresponding to the dark areas in Fig. II. C, C. Erosions at margin of articular cartilage. Fic. 1V.—Spavin. Section through the lower tarsal row and metatarsus showing condensing ostitis, with marked osteo-sclerosis in tarsal bones. Williams, Fisher, and Udall : The Spavin Group. 7 - necrotic and fallen into the cavity, or the red marrow may proliferate, and a mass consisting of connective tissue, vessels, and lymphoid marrow cells completely occupy the cavity if the superficial layer of cartilage remains intact. The amount of necrotic tissue débris is unusually abundant in Figs. II and III at C, If the superficial cartilaginous layer has broken down com- pletely and the excavation has acquired an opening into the articular cavity, the granulation or marrow tissue may grow up into the joint cavity, and, meeting there with prolongations from corresponding erosions in the opposing bone, the two may fuse, producing fibrous anchylosis which constitutes in a measure a reparative process. The reparation of the affected parts is largely a reversal of the processes just outlined. The bone cells, lymphoid marrow cells or osteoblasts resume their normal properties, the osteo- clasts largely disappearing, new osseous lamella form about the Haversian canals, new lacunz and canaliculi appear, and instead of rarefying ostitis, we observe an ostitis condensans, which generally more than replaces the prior bony lamella, producing an osteo-sclerosis as shown in Fig. IV, in which the former porotic bone has become exceedingly dense, almost like ivory. ‘This represents the recovery of the osseous lesions in the most complete form we are able to recognize. If the marrow cavities which we have described push their way near to or upon the surface of the joint and ossification of these prolongations take place, they cause hard, rough, pointed elevations or calciffed points, readily felt in some, cases upon the joint surface, and capable of causing friction erosions on the opposing articular surfaces. Following the fibrous anchylosis, the prolongations tend to become ossified, producing an osseous anchylosis of varying degrees of completeness. Rarely the entire joint surface be- comes denuded of articular cartilage and the anchylosis may then become complete, but generally there are islets of articular cartilage of varying sizes, which leave the anchylosis incomplete, and according to incompleteness, insecure, exposing it to inter- ruption or fracture resulting in a renewal of pain and lameness. In other cases the prolongations of red marrow with their vessels and connective tissue fibers fail to fuse with those from the opposite joint surface, but push against them and into any depressions or cavities in the opposing surface, the prolongations 8 Williams, Fisher, and Udall: The Spavin Group. being irregularly conical, the projections from the two opposing surfaces alternating and interlocking in a way. to produce 4 false anchylosis competent to fix the joint to a limited degree without giving the security of a true and complete fusion. PERIOSTITIS AND ExostosEs. As we have already ‘suggested, the ostitis is general, with here and there points of special virulence which determine gross lesions. These areas of inten- sity are not always subchondral, but are possibly even more frequently subperiosteal, leading to the formation of exostoses, which constitute the most universally visible lesions of the malady. In many cases the subchondral and subperiosteal lesions are simultaneous, as is shown in Fig. V, where the destruction of the articular cartilage and the exostoses are equally prominent. In other cases, as seen in many peri-articular ringbones (Fig. VI), the areas of intensity are chiefly subperiosteal and the articular cartilage largely escapes destruction. When the in- flammation involves the periosteum, it is generally in the immediate vicinity of the attachments of the capsular ligaments. Instead of the destructive processes, we have outlined in the osseous tissue, the periosteum, when the seat of the disease, tends to a productive inflammation. The deeper osteogenetic layer assumes increased activity, the osteoblasts multiply, and new osseous tissue is rapidly formed. The Haversian canals extend outward from the normal into the new formed bone. The new osseous tissue possesses all the essential characters of normal bone, but the regularity is disturbed in various ways. The Haversian canals are larger and more irregular in arrange- ment, the new bone is softer and more fragile. Its outline dur- ing life appears somewhat smooth and regular, but when the affected bones are macerated and the connective tissue removed, the surface is found to be very irregular with many deep inden- tations passing into the exostoses, dividing them up into irreg- ular adherent bony masses. The new formed bone tends finally to undergo osteo-sclerosis when the active stage of the disease has passed, and may in time atrophy. Synovitis. Synovitis is a well-nigh constant condition in this affection, and while it apparently bears a close relation in- many cases to the usury of the articular cartilage, this does not seem to be constant, nor can synovitis be recognized in all cases, either intra vitam or post mortem. Fic. V.— Humero-radial and femoro-tibial articulations, showing extensive disease, with deep erosions and abundant marginal exostoses. The specific gravity of these bones is greatly decreased. Fic. VI.—A series of ringbones, showing in the two upper rows the interphalangeal articular surface, with erosions ; and in the lower rows the same specimens showing the exostoses. Fic. VII. —A series of navicular bones, showing variations in erosions, pit-like excavations and exostoses. Fic. VILI.— Femoro-patellar articulation (gonitis), from Case IV. S. M., Synovial membrane, thickened and tufted. N, Calcified nodule in the walls of the articular capsule, from which sus- pended by a narrow neck, 1s a second nodule, N’, which might readily become a floating body. E. C, Diminutive and flattened external femoral condyle, between which and the enlarged internal condyle, I. C., the trochlear groove is practically wanting. P, Patella, showing at E, an extensive erosion, caused by friction in passing out and in over E. C, at E’, the result of ‘‘ floating disloca- tion of the patella.” | Fic. IX. — Gonitis and floating luxation of the patella in eighteen-months colt. - I. Normal femur. II. Diseased femur from Case IV, showing another view of the femur ir Fig. VIII. A, External condyle. B, Internal condyle. a In I, the external condyle is sharply defined and well elevated above the sulcus, while in II the condyle is rotund, flattened with almost no depression or groove between it and the internal condyle. The differences between the two internal condyles is very much greater. The normal (I) is well- defined and sharp, while the diseased (II) is greatly enlarged, puffed up, and undulating at its upper part. There is in JI no trochlear groove in which the patella may glide, and no external trochlear ridge to guide it; hence patella slipped out and in position at each step. Williams, Fisher, and Udall: The Spavin Group. 9 It is most apparent when the intense areas of the disease involve an important articulation. The character of this synovitis has been in controversy. Many of the older authors speak of this affection in a general way as arthritis sicca or dry arthritis, but, when they do so, they have in mind, apparently, only those joints of limited motion and scant synovia. It is essential for repair in cases of developed spavin or ringbone that eventually synovia should cease to be secreted in order that contact’ of the denuded bones may occur and permit anchylosis. In these articulation there are only very limited synovial sacs incapable of distension, and severe inflammation apparently quickly des- troys, or diminishes, their secretory power. In the larger artic- ulations with extensive synovial sacs, the secretion -becomes very greatly increased. In many cases of spavin, presumably without erosion of the cartilage of the tibio-astragaloid articu- lation, the synovial sac of this joint is greatly distended, con- stituting what we may well term a false bog spavin in contra- distinction to the generally greater distension of the joint, some- times unaccompanied by lameness, or, so far as we know, by any osseous disease, to which we ordinarily apply the term of bog spavin. Ths distension serves to cover and disguise the exostosis of spavin and in this way tends to lead to error in diagnosis. It is a part of the one affection, the synovitis of ordi- nary spavin having the same etiology and prognosis. + Still more pronounced, and quite characteristic of the malady, is the synovitis in gonitis. There the distension of the femoro- patellar bursa is, next to the lameness, the most prominent sign of the malady and, moreover, its results are serious for the integrity of the articulation. When occurring in young animals, the extreme distension of this sac lifts the patella upwards and forwards, until it is above the external trochlear ridge, inducing a floating dislocation of the patella, as seen in Figs. VIII and IX. The floating patella is drawn outwards over the external ridge by the biceps femoris and other muscles during flexion, and inwards again during extension, the result- ing attrition wearing away the cartilage and bone from the summit of the external trochlear ridge and from the median ridge of the patella, as shown at E and E* in Fig. VII. The increased pressure upon the summit of the ridge, the disuse of the trochlear groove and the internal ridge, along with the disease processes, taking place within the articular 2 10 Williams, Fisher, and Udall: The Spavin Group. end of the bone, bring about serious deformities in the joint. The external ridge loses its cleanness of outline, flattens down and becomes practically level with the bottom of the sulcus, while the internal trochlear ridge puffs up, enlarges in every direction, is rounded and obtuse everywhere; the trochlea has lost its function as a conduit for the patella and the efficiency of the joint is permanently and incurably destroyed. Compare Figs. VIII and IX. If we examine one of these articular cav- ities, it is found filled with an excessive amount of transparent or semi-transparent, faintly reddish or yellowish, thin synovia. The synovial papille are hypertrophied, greatly thickened and elongated, as shown at SM in Fig. VIII, and’ some of the more prominent are calcified at their free extremities, as shown at N, while another nodule, N+, is attached to it by a narrow neck, which time or accident may cause to part, and a free body in the joint result. In many cases the articular capsule is thickened and indu- rated, sometimes becoming enormously so to the extent of one- half to one inch of dense fibrous tissue, and, rarely, within this dense mass may be found large masses of necrotic tissue debris, as shown in Fig. II at D D. The following portions, to and including page 2098, is an ab- stract of the thesis already referred to. The outline of the work was planned by Professor W. L. Williams, and the microscopical technique largely under the supervision of Professor: V. A. Moore. MatertaL AND MerTuHops or Invesrication: — In the investi- gation of this disease we have had recourse to the clinical cases of the New York State Veterinary College. The material for both clinical and post mortem examination has been more than sufficient to occupy the available time devoted to the work. In some cases the history of the patient has been somewhat deficient, yet enough has been given with the majority of them to trace the origin and character of the clinical symptoms. The following scheme has been employed as a working basis, but the amount of time required for carrying out the experiments has of necessity confined us to a limited portion of the original outline. Williams, Fisher, and Udall: The Spavin Group. 11 I. Gross examination. A. Physical. (a) History of animal. (b) Character of lameness (local, general). (c) General condition of the patient. B, Anatomical examination of joints and extremities, (a) Amount and character of synovial fluid. (b) Character of synovial membranes and capsular ligaments. (c) Condition of articular cartilage. (d) Character of deformity. II. Urine analysis. (a) Determination of reaction. (b) Amount of phosophates and other solids. III. Pathological examination of the tissues. A. Bone (macroscopic and microscopic changes). Preparations of bone for microscopic examination were made in the following manner: Small pieces of fresh tissue were fixed in an alcoholic-sublimate solution, or in picric alcohol; these were hardened in ethyl alcohol by placing them first in that of fifty per cent. strength, then removed to that of sixty-seven per cent., eighty-two per cent., and ninety-five per cent. respectively ; the hardening process being complete in from three to five days. Specimens that were fixed in the alcoholic solution of corrosive sublimate and hardened in alcohol were employed for filed prepa- rations, which were excellent for demonstrating the inorganic structure of the bone. To bring out the structure of both the organic and inorganic tissue it is necessary to decalcify. The following fluid was used for this purpose: sixty-seven per cent. alcohol, ninety-seven parts; concentrated nitric acid, three parts. The methods of technique may be found in “Normal Histol- ogy,” Piersol. The sections were stained in hematoxylin and picro-fuchsin and mounted in Canada balsam. Several other stains were used, but the above were the only ones that gave satisfaction. EXAMINATION OF SUBJECTS. Case 1.—A bay mare fifteen years of age, brought to the clinic in the spring of 1900 to be treated for lameness in the right hind limb. Symptoms; anemia; slight ventral hernia; lameness very marked, especially in the hind limbs; well developed gonitis on the right side; upon urging the animal to trot she appeared to be lame in every joint. Autopsy:— Left anterior extremity: scapulo-humeral articulation; the articular cartilage was roughened on the head of the humerus; the syno- vial membrane discolored.. Elbow joint: the cartilage on the trochlea of 12 Williams, Fisher, and Udall: The Spavin Group. the humerus contained an ulcerlike depression, one-half by five-eighths of an inch in size; a similar roughness was present on the articular surface of the ulna. Carpus: cartilage slightly eroded between the articular surfaces of the os magnum and radius, and between the small carpal and metacarpal bones; on microscopic examination the cartilage was found torn, villous, and fibrous; the cartilage cells proliferated and enclosed in mother capsules. The osseous tissue of the os magnum was abnormally hard and many of the marrow cavities were empty, while others were completely filled with marrow cells; the canaliculi of the lacune had undergone marked atrophy, this was also true of the protoplasmic ex- tensions of the bone corpuscles; many of the bone corpuscles (cells) within the lacune assumed a roundish form. : Right posterior extremity: femoro-patellar articulation: the synovial fluid had increased in amount; the articular cartilage presented extensive erosion on the inferior surface of the patella; the entire surface of the fibro-cartilaginous process eroded; the corresponding surface of the femur had undergone similar changes but not discolored. Femoro-tibial articulation: cartilage extensively eroded, in places the atrophy was com- plete. One of these areas presented a polished surface one and one-fourth inches by three-fourths of an inch in diameter, portions of the cartilage in places had undergone osseous degeneration. The histological changes identical with those of the carpus; metaplasia of the cartilage matrix and arrangement of the proliferated cartilage cells in mother capsules. Tarsus: cartilage absent over a small triangular area on the distal extremity of the tibia; bony exostosis in the form of a spavin. Fetlock: discoloration and roughness on the internal condyle of the first phalanx. Left posterior extremity: femoro-tibial articulation: cartilage rough- ened; synovial membrane discolored; capsular ligament thickened; the histological changes were the same as previously described. Tarsus: tibio- astragaloid articulation: normal. Astragalo-scaphoid articulation: car- tilage atrophied in the form of erosion-like ulcers that reach to the bone; bursa of cunean tendon normal. Fetlock: cartilage and bone normal: tendon sheaths discolored. Conclusions; An examination of the bones of this animal suggested that the diseased processes were well advanced. Exostoses and pro- liferative changes in general seem to have reached a termination; the solidity of the bone itself and appearance in the marrow cavities indicated a condensing stage of the disease. Although a few of the marrow cavities, were entirely filled with cells the greater number were comparatively empty so that large open spaces were visible. (Figs. X and XI.) Case II.—A small bay mare, advanced in age, brought to the clinic to be destroyed because of chronic navicular disease. Clinical examination revealed no exostoses. Autopsy:— Right anterior limb: bursa podotrochlearis: cartilage and tendon roughened, the bone was also affected. Suffragino-coronal articu- Jation: the proximal extremity of the second phalanx presented areas of discoloration near the center, upon removal of the apparently normal car- tilage these punctiform areas were seen to be present in the bone. Left anterior limb: articulations apparently normal. Bursa podotro- Fic.X. —Section through cuneiform magnum and medium, demonstrating osteo-sclerosis and 9 anchylosis. a, Marrow cavities containing relatively few marrow cells. B, C, Articular cartilage, D, Lacunz, many of which contain no bone cells. x, Norma bone cells x, 50, Case No, I. = Fic. XI. — Section through cuneiform magnum and medium, demonstrating osteo-sclerosis and anchylosis. x, 450. A, Marrow cavity containing relatively few marrow cells. B, Articular car- tilage. D, Lacune containing no bone cells. x, Lacunz containing bone cells; atrophy of the cells and canaliculi are common. Case No. I. Williams, Fisher, and Udall: The Spavin Group. 13 chlearis: the tendon over the navicular bone was extensively roughened. Posterior limbs: small nodular exostoses were found in the region of the tarsal joints; firm anchylosis of the cuneiform magnum and medium, the latter also anchylosed with the metatarsi. Cunean bursz obliterated, there being a firm union between the tendons and the bone. Case III.—A thirteen year old mare. Eight years ago she suffered from lameness of the anterior limbs, and although vigorous, stumbled frequently when driven. This condition was present up to the time of death. Disease of the hind limbs was not diagnosed during life. Autopsy; —Right anterior limb: scapulo-humeral articulation: car- tilage slightly roughened over the head of the humerus, it appeared to be roughened and thinner than normal. Carpus: cartilage covered with uulcer-like depressions between the upper row of bones and radius, small pieces of fibrous tissue floated in the depressions; slight lesions present on the distal end of the metacarpus. Right hind limb: femoro-tibial articulation: articular cartilage almost completely atrophied over the median trochlea of the femur; the latter bone was very porous at its distal end, the handle of a bistuory could easily be pushed into the osseous tissue for a distance of one and one- half inches. Left hind limb: femoro-tibial articulation: lesions allied to those found in the corresponding limb, the trochlea of the femur was less porous. Case IV.— Patient presented at the clinic April 3, 1900, when the following notes were made: age one year, diet four quarts of oats and ten pounds of hay daily. Patient to be treated for gonitis first noticed about April second, and from which the animal appeared to be very lame. Clinical examination’ revealed one gonitis, two spavins, and four ringbones. This animal was killed in December of the same year because of a chronic luxation of the patella. Autopsy: —Left hind limb: femoro-patellar articulation: synovial membrane distended with a large amount of fluid; extensive thickening of the capsular ligament; erosion of the external trochlea of the femur and roughness of the internal condyle. The external trochlea very compact, the inner soft and porous. Femoro-tibial articulation: the changes were similar to those in the preceding. Free bodies were found in the joint composed of bone, cartilage, and connective tissue. Histological examina- tion; the trabecule and osseous portions of the marrow cavities well marked, the latter containing many giant and lymphoid marrow cells. The giant cells were not all in direct contact with the trabeculz, some were situated in the middle of the marrow cavity. Tarsus: bones apparently normal; the cartilage exhibited small, punctiform, reddish-blue spots about two millimeters from the external margin of the articular surface. These correspond to those mentioned by other investiga- tors (“points of contact” of Eberlin). Upon a histological examin- ation of a section made through one of these points the following conditions were noted: the cartilage cells grouped in an irregula man- ner, their form more rounded and somewhat larger than in a like section of normal bone. An empty cavity was noted between the cartilage and 14 Williams, Fisher, and Udall: The Spavin Group. bone (Fig. XII), which may be due to mechanical manipulation of the tissue. The following changes were noted in the bone: the canaliculi of the lacune entirely atrophied in the region of the empty space (Z), the lacune roundish in form, the marrow cavities completely filled with cells and capillaries (Fig. XII, D1). The bone apparently in a condition of active hyperemia; obviously a case of osteo-porosis in the early stages. Case V.—A bay gelding draft horse twenty years old, bred and raised upon the University farm. The diet consisted of hay with five pounds of corn and oats mixed night and morning, and five pounds of oats at noon. The animal had always been vigorous and in excellent health. April seventeenth, nineteen hundred, he was presented to the clinic to be treated for lameness in the hind limbs, which had come on gradually, and at times was not noticeable. Diagnosed as gonitis. The following October the animal was returned to the clinic without improve- ment and owing to his age and severe lameness was left for disposal. Autopsy: — Pronounced changes were found on the proximal extremi- ties of both tibial bones; articular cartilage entirely absent from median side of left tibia, around this area the cartilage was very much thickened. Exostoses in the form of nodules were abundant around the articular sur- faces, some were firmly attached while others were held in place by fibrous tissue. The articular cartilage of the condyles of the femur presented a rough appearance; slight abrasions were found in some of the other joints. Histological examination, thin sections from the proximal extremity of the tibia presented bone and cartilage undergoing rapid and complete degeneration (Fig. XIII); the solid bone matrix: (trabecule) had lost nearly all of its characteristic structure; the lacune were.entirely absent over a great extent of the sections examined. Just beneath the abraded cartilage (Fig. XIII, A) the changes were very marked, only an occasional round space indicated the presence of a former lacune. The marrow cavities visibly enlarged and entirely filled with marrow cells, among which were many giant cells (Fig. XIII, D); ‘Howschip’s lacune were abundant. Examination of this bone with a microscope that magnified fifty diameters revealed many places where the marrow cavities and trabecule had a very similar appearance; the cavities were so completely filled with cells and capillaries, and the bone had lost so many of its typical features that a higher magnification was necessary to determine the exact location of the boundary line. In certain of the marrow cavities reparative pro- cesses were beginning to take place. Marrow cells that had the appearance of osteoblasts in developing bone of young animals were arranged around the periphery of the cavity in contact with the bone trabecule. Blood vessels and connective tissue were present as in the reticular tissue of normal bone marrow, the amount of such connective tissue, was, however, abnormally small. The areas in which reparative processes were taking place were very small in comparison with the whole amount of diseased tissue; they were very suggestive, however, of the method by which such osteoporotic bone may become hard again, and finally pass to osteo-schlerosis. num ofa yearling porosis in the early stages from the os mag Fic. XII.— Demonstrating osteo~ colt. X,50. Case No. IV. A, Cartilage cells, round in form and irregularly grouped. B, Cartilage. D, Bone. D/, Marrow cavities, completely filled with cells and capillaries. = < S23 328 Ore vou dae Bee co es -voe a 3 SE bo ge Se aod See av Bog oeS cog ako ase oS on 9 avis are c go 328 eo.8 On e= 5 oe ag ono} ey gad oes $e". Path de = 8 ba ge §$ ago one ad oes a35 eiehae ata “ge Gos aA gad a 825 vo bok oo 3 ho ao iS eano, oe bo 2a¢6 20°98 a - Re Ss o pee we 8 £43 Pee Sms nino peo eS a 2 oF ecletan S35 ORO” of oF oo PVD G 20S 8 £500 Poe eves 4ow? Cod _ a3 5M £ % 5 = A Fic. XIII. Howship’s lacunz. These ar cells and vascular structures of the articular cartilage. Fic. XIV. — Proximal extremity of the tibia, showing extensive osteo-porosis. A, Marrow cells. B, Osteoclasts (giant cells). C, Bone matrix. D, Lacune, in which canaliculi are absent, bone cell having undergone almost complete atrophy. F, Howship’s lacune. This drawing is made from the same section as Fig. XIII, Case V. X, 450. the tibia, showing extensive osteo porosis. A, Lacunz, C, Bone cell. D, Bone matrix (trabeculz). E, Line of Fic. XV. — Proximal extremity of B, Canaliculi extensively atrophied. contact between bone and marrow. and F. X, goo. F, Marrow cells. X, Marrow cavity; note similarity of C Bile: We Ee): & S § Sia ( & Ng f i Qt years. A, Cartilage cells. C, Boundary D, Marrow. E, Tella ossea. X, 50. Fic. XVI.— Healthy scaphoid of horse ; age 12 between articular cartilage and bone. Williams, Fisher, and Udall: The Spavin Group. 15 A glance at the cartilage of this tibial bone shows that it was extensively diseased (Fig. XIII). The cells are arranged in mother capsules and variable in size; near the free surface of the cartilage they are greatly modified in structure and arrangement. In certain areas the cells are larger (Fig. XIII, E'). The con- _ nective tissue between the cells is increased in amount and _ fibrous in character, while normal articular cartilage is of the hyaline variety. In places we find a metaplasia of the cartilage with splitting of its fibers, in other places the cartilage has en- tirely atrophied, bringing the abraded articular surfaces of the bones in direct contact. The condition and appearance of the bone and marrow in this section offers a suggestion to the influence exerted by the giant cells (osteoclasts) upon bone resorption. This is the only case in which we have been able to demonstrate the presence of such cells in large numbers, only a few being observed in case IV. In case V, however, they were very abundant both in Howschip’s lacunze and in the center of the marrow cavities. Certain parts of the sections examined presented areas where no giant cells were visible, the marrow cavities were rich in a cellular structure, and the bone matrix presented marked indications of resorption. The lacunz were misshapen or rounded, some were very much enlarged with ‘irregular and poorly defined outlines, others ab- normally small: The bone cells in such lacunze were hypertro- phied, atrophied, or absent. In the majority of cases noted they were present, enlarged, and granular in appearance, their posi- tion in the bone matrix alone, distinguishing them from neigh- boring marrow cells (Fig. XIV). While it is generally believed that the osteoclasts exert a certain influence in bone resorption we have a case where it would seem that resorption was rapidly progressing in their absence (Fig XIV). It is difficult to understand just how the osteoclasts can bring about such marked changes in the bone cells that are deeply situated in the bone matrix; the idea suggests itself that the primary change begins in the individual cells themselves, those of the trabeculz, as well as in those of the Haversian canals. As the bone tissue atrophies it is perfectly logical that the Haversian canals should become enlarged. Sup- pose in Fig. XIV, for example, that three or four of the bone corpuscles continue increasing in size until they occupy a common space, and that at the same time this. breaks through into the 16 Williams, Fisher, and Udall: The Spavin Group. neighboring marrow cavity; such changes would result in the formation of a Howschip’s lacuna. Summary. — This group of: diseases is characterized by an inflammation of the bone, cartilage, and capsular ligament. The following changes are noted in the bone: hypertrophy of the marrow cavities, and atrophy of the osseous matrix. The mar- row cells are greatly increased in numbers. The bone cells (corpuscles) become granular in appearance and smaller in size. The lacune are enlarged, and at the same time may lose their typical form. The canaliculi undergo partial or complete atrophy. The disease process seems to be operative throughout the whole ’ extent of the affected -area at the same time; that is, bone resorption is not confined to those portions of the osseous matrix with which the marrow cavities are in direct contact (osteo- myolitis), but progresses just as rapidly within the interior of the compact bone (ostitis). These changes are found in the bone during the earlier and more active stages of the disease (osteo-porosis). They are demonstrated in figures XI, XII, XIII, and XIV. During this stage the bone is abnormally soft, porous, and light (osteo-porosis), later becoming more compact and heavier (osteo-sclerosis). The histological characteristics of osteo-sclerosis (condensing ostitis) are atrophy of the marrow cavities and hypertrophy of the bone matrix; the-cellular struc- ture of the marrow cavities becomes greatly increased in amount (Figs. XI and XIII). There is a cessation of the inflammatory process; and resorption of bone is replaced by a regeneration of the osseous structure. Many of the lacunz, however, fail to regain their lost bone cells (Fig. X, d). The disease of the bone has been accurately termed: ‘“‘ Osteo-porosis succeeded by os- teo-sclerosis’’ (Gotti, Bayer, Frohner, Eberlein, etc.). The characteristic changes in the cartilage are: fibrillation of the superficial layers, extending in some cases to the osseous tissue; hypertrophy of the intercellular matrix, as well as hyper- trophy and proliferation of the cartilage cells; partial or com- plete atrophy of certain portions of the articular cartilage charac- terized in some cases by the formation of ulcer-like depressions (Figs. XII and XIII). The capsular ligament presents the most pronounced changes in those articulations of which the knee joint is a type. In cer- tain cases, especially in the earlier stages of the inflammation caused by this disease, the capsular ligament is distended with an ‘ Williams, Fisher, and Udall: The Spavin Group. 17 abundant serous exudate (serous arthritis) ; bluish-red discolor- ations of the serous membrane are observed. As the disease ad- vances one finds connective tissue proliferations and osseous degeneration of the ligament (arthritis deformans). In many cases these degenerative proliferations become constricted at their points of attachment to the capsular ligament and drop into the articular cavity where they are found as free joint bodies (Case No. V, femoro-tibial articulation). It will be seen that this disease has many lesions in common with arthritis deformans as described by Fréhner: “In human surgery deforming inflammation of the joints is a chronic, aseptic, senile arthritis (malum senale) which leads to severe and permanent changes in the entire joint. It is not character- ized by suppuration; it may have a spontaneous or traumatic origin; is either mono- or polyarticular; its favorite seat is in the joints of the knee, hip, shoulder, and elbow, on the fingers, and in the vertebral column. It is a non-febrile arthritis that is ushered in with stiffness, crackling, and slight pain in the in- volved joint; usually continuing during the life of the indi- vidual, and finally leads to deformity of the entire joint. Anatomically it consists of degeneration and new formation processes of the cartilage, bone, and joint capsule. ““(a) In the articular cartilage one finds changes character- istic of arthritis ulcerosa.sicca chronica; namely, fibrillation of the superficial layers, focus-like areas of fibrillation and soften- ing of the deeper layers, ulceration, and even complete atrophy of the cartilage with the formation of smooth, polished surfacés. One also finds active proliferation of the cartilage in the form of nodular processes. “(b) In the bone there exists a subchondral inflammatory osteo-porosis with atrophy of the lacune in addition to bony new formation. ‘““(c) The joint capsule shows proliferation, thickening, and wrinkling. One occasionally observes the formation of free joint bodies.” (Bayer-Fréhner “ Tierarztliche Chirurgie und Geburts- hilfe Allgemeine Chirurgie,” 1905.) — While this group of diseases, of which spavin is a type, bears a very close resemblance to arthritis chronica deformans, there are certain features that are not characteristic of the latter affec- tion; namely, in the spavin group the changes in the first stages of the disease are confined largely to the bone (Fig. XII). In 18 Williams, Fisher, and Udall: The Spavin Group. arthritis deformans the cartilage is the primary seat of the prin- cipal changes. In view of these facts Professor Fréhner defines spavin as follows: “Spavin is principally an ostitis of the os magnum-and medium as well as the metatarsus, from which there afterwards secondarily develops a deforming inflammation of the tarsal joint. It is more correct, therefore, to define spavin as an osteo-arthritis chronica deformans.” (‘‘ Allgemeine Chirurgie,” 1905.) The same term is applied by this author to the changes which, occur in ringbone, gonitis, omarthritis, etc. It is obvious that the lesions found in the preceding five cases are in accord- ance with Professor Frohner’s interpretation of the disease. It is further noted that, similar to arthritis chronica deformans in man: “it may have a spontaneous or traumatic origin.” Further investigations may reveal that the influence of traumata, as direct causes of the disease, has been somewhat over-rated. In cases III and IV the existence of a spontaneous (pathological), in- direct etiological factor seems to be fairly well demonstrated, being present in both a young and an old animal; many careful and widely distributed examinations are necessary to determine the extent of this influence. The causes of “ osteo-arthritis chronica deformans,’ when of “pathological” origin, lack complete and unobjectionable demonstration. Rachitis and rheumatism are doubtless operative in many cases of the disease when occurring: in young animals; the latter may be a more important factor than is generally al- leged (“‘ Monatshefte fiir praktische Thierheilkunde,” Vol. XV, page 211: “ Rachitische Schale und rachitischer Stelzfuss beim Pferde:” Fréhner). This pathological condition is not confined to young animals. The visible lesions may be confined to one or two bones and articulations, or be well distributed through those of the extremi- ties. Clinical examination may lead to diagnosis of lameness in the anterior limbs when a post-mortem examination of the same animal shows that the disease is more pronounced in the posterior limbs (Case IIT). URINALYSIS. The composition of the urine during this affection has not been fully investigated, nor have definite observations been made Williams, Fisher, and Udall: The Spavin Group. 19 regarding the volume or density of that excretion. We became interested in relation to the amount of phosphates occurring in the urine of animals affected with this disease as compared with those in apparent health, but failed to carry these investigations to a conclusive stage. The few data are highly suggestive, how- ever, and should stimulate further study. The following table exhibits graphically the results of the few analyses made by Prof. Geo. W. Cavanaugh relative to the phosphoric acid (P20s) in the urine. Laboratory Phosphoric Acid Number of Condition of Animal per Liter of Analysis Urine 2,672 Slight double navicular disease traces 2,673 Non-diagnosable shifting lameness (Rheumatism ?) -| no trace 2,674 Healthy farm horse....-.ecesseeeeeeeececcesesece ++| no trace 2,675 Healthy farm horse ..-+sseeesses ence cence eeeeeee «-| no trace 2,676 Weanling colt with four active ringboneS.-....---eeeeeeeesereceeere 4.55 grammes 2,677 Same patient after an interval of eleven days..-..-+++esseereereeeeee 3.76 grammes 2,678 Second sample from 2,673 (was being fed phosphates in large’ quan- tities)se cs cereceenncecee eens ce ccnntecsnseneasansanstesnacsneenes -09 grammes 2,679 Second sample from 2,674 (was being fed phosphates in large quan- tHitIES) 0 onc ce nie cacenein eecleveines sian escesd ieeneute ee rreeneen seenene trace These fragmentary records serve to indicate that during the active stages of ringbone. and navicular disease an excess of phosphorus, presumably in the form of calcium phosphate, is present in the urine. It occurs only in traces in 2,672, the mare at that time having been under the best possible hygienic condi- tions as understood by us, and the presence of the malady barely recognizable in a short gait without limping. In 2,676 and 2,677 the amounts of phosphates become very marked and stand out as distinctly pathological when compared with the other analyses. The case, a weanling filly, was suffering acutely with four active ringbones from which she recovered her general condition and now, after eight years observation, is working sound, the large ringbones being quiescent. In sharp contrast to these are samples 2,673, 2,674, and 2,675, the first of which had a peculiar, intermittent lameness for a year or more, shifting from region to region without apparent * cause, or without inducing any recognizable lesions in any part and ended by apparent recovery which has remained constant for eight years. Nos. 2,674 and 2,675 were healthy farm animals employed at regular farm work. An interesting query is here raised upon which chemists seem to be at variance, some claiming that phosphates are not normally 20 Williams, Fisher, and Udall: The Spavin Group. excreted in the urine of the horse while others are insistent that it is so excreted in measureable quantity. It would appear that one of the great difficulties in the analysis of the urine of the horse is an attempt to apply the methods used in examining the urine of man, especially quick, approximate methods which yield reasonably accurate results, or rather estimates in human urine, and which may be in part or wholly invalidated by the widely - dissimilar character of equine urine. Have the different. investi- gators dealt with urine of essentially different composition? Was that urine which contained phosphates normal? In the fore- going we find in acute ringbone a maximum of 4.55 grammes of phosphoric acid (P205) equivalent to 10.18 grammes of calcium phosphate (Ca3(-PO4)2) and then meet with complete negation in normal work animals. Another interesting feature is the effect of the feeding of large quantities of phosphates upon their excretion by the kid- neys. After the animals from which samples 2,673 and 2,674 were taken had later been given two to three ounces daily of sodium phosphate in their food, the former showed .og grammes of P2O5 per liter of urine or .02 of the quantity observed in 2,676, while the later, 2,674, showed only traces of phosphates. This would appear to suggest that the ingestion of an unusual amount of phosphates tends to establish or increase their presence _ in the urine, but only very slightly as related to the amount in- gested, most of it evidently being excreted by the intestinal tract’: or other avenues of egress. Urinalysis appears to be a most inviting field for the further study of this malady. ETIOLOGY. As most authors consider the entire group to be so many distinct affections, they attempt to elucidate separate causes in each instance, and in so doing have invoked for each, almost every conceivable form of mechanical insult and other injuries. Confessing the identity of the lesions, wherever they may ° occur, we should admit a cosmopolitan reason for their existence, _ which would serve equally to explain spavin, navicular disease, ° fracture of the ribs, anchylosis of the vertebrz, or any other member of the group. As an illustration we might take the horse .from which Figures XVII and XVIII are taken. Here *w1qoz19A JequIN] pue [esiop 94} uodn sasojsoxa pue jo sisojAyoue pue plowesas ‘syoo]39j JOL1eqUe YIOg Ie SITUISLA-Opua} e19Aas pry juarjed ay} op pasojAyoue pue sqti painqoesy Suroys ydessojoygd—IIAX “A “949 ‘souoqapis ‘asvasip Je]noAeu ‘squoqsull ‘s ) ainjoely snoauejuods ay} YI Zuoje A “B14 se 9s10y aes WOly w1qgayloA Jequin]-ost 21u0WNaUd SNOrse}UOD BUIMOTIC Fic. XVIII. — Sections of foot from the same case as Fig. XVII. II. Cross section of os suffraginis near its superior end. O. S., Os suffraginis. Ex., Exostosis on os suffraginis (ringbone), tending to envelop the three flexor tendons. F.C., Flexor of the corone. F.P., Flexor of the os pedis. F.S., Flexor of the suffra- ginis (suspensory ligament). Longitudinal section of the left half of fore foot. O.S., Os suffraginis. R.B., Ring- bone on os suffraginis. O.C., Os corona. S.B., Sidebone. Ex.N., Exostosis on navicular bone. O,N., Navicular bone. O. N. C., Articular cartilage of navicular bone. O.P., Os pedis. A. and B., Arteries. 1 Williams, Fisher, and Udall: The Spavin Group. 21 we have shown ringbone, sidebones, navicular disease, sesamoi- ditis, vertebral anchylosis, and thirteen broken ribs. Although no detailed autopsy was made and the diseased parts noted were only incidentally discovered while examining for tendonitis and tendo-vaginitis, it is fair to assume that other parts of the skele- ton were similarly involved. 1t would be absurd in this case to refer the sidebones to concussion from the shoe heels, the navicular disease to shoeing with too low a heel, the ringbones to strain of the lateral ligaments, the sesamoiditis to concussion, the tendonitis to strain, the spinal anchylosis to unobserved slip- ping in the stall and the thirteen fractures of ribs to as many blows from a rough groom or horseshoer. Coming simultane- ously as these did, and maturing within a few weeks without the action of any of the foregoing causes, so far as can be deter- mined, we are forced to look for a cause which will afford as good an explanation for the broken ribs as for the navicular disease. The alleged causes of the different members of this group of affections are so numerous and varied that we cannot fully con- sider each in its relation to the etiology of others, but must rather content ourselves with a brief study of the relation of those factors indicated as the essential element in the etiology of one member of the group to the causation of the others; that is, we desire to study the etiology of the group as a group and not become misled by what may appear as essential causes in one member which could not have any influence upon another. The principal cause assigned by veterinarians for this affec- tion is traumatism, rarely some constitutional disease of the bony skeleton or of the general system, and occasionally heredity is charged with a very important rdle. Strain. Among the trauma, strain holds perhaps the first place as an alleged cause of this disease, and this form of trau- matism being generally considered so common and _ universal renders it a very convenient and ever-present means of explana- tion. In order to fully consider this allegation, we need first to study the mechanism of the limbs of the horse, the parts most frequently and most evidently affected, and learn how. far the ligaments of these articulations are subject to injury as a result of over extension in the direction of their fibers; and secondly, to inquire what actual evidence can be adduced as to the fre~ 22 Williams, Fisher, and Udall: The Spavin Group. quency and extent of these injuries. Were the question pro- pounded, in what two animals are strains most common; doubt- less the uniform answer would be, man and horse, some placing the one, some the other, first. Carefully examined comparatively, they represent the extremes in anatomical structure and attitude among the higher mammalia. Comparing the thoracic limbs of the two, we find in man a member adapted for the prehension and holding of objects, for climbing and for more or less suspending the body; while in the horse it is used essentially for weight bearing, supporting fifty-five per cent. of the body weight, and plays a fundamental part in the process of locomotion. In man it is rigidly attached to the thorax by means of the clavicle, while its sole attachment in the horse is by means of powerful and elastic muscles, with the heavy skin covering, which permits extensive movements of the member upon the chest. The scapulo-humeral articulation of man, with the support of the clavicle, stands out prominently from the thorax with the humerus free and the joint so formed that a very extensive area of motion, representing a hemisphere, is permitted. In the horse, on the other hand, the extensive flattened contour of the scapulo-humeral region with the angle existing between the two bones closely applied against the chest walls, prohibits in a large degree rotation, adduction, and abduction, and limits its move- ments in health chiefly to antero-posterior flexion and extension, so that direct strain upon the ligaments, originating in the humerus itself, is practically prohibited, while strain upon the joint transmitted through the radius is usually nullified by the free movement of the shoulder on the chest wall or by closure of the scapulo-humeral angle, each of which safeguards are denied to man. As a result of the formation of the shoulder man suffers rather frequently from severe strain or dislocation of that joint or fracture of the clavicle from violent impact on the humerus, while in the horse these accidents are rarely diagnosable, the dis- location of the scapulo-humeral articulation occurring so rarely that few practitioners see cases. Since dislocation must always constitute the finality of the strain of articular ligaments, its frequency serves as an index of the occurrence of the latter. Examining the limb as a whole, we find that in man it is capable of extension in a straight line from end to end, resulting Williams, Fisher, and Udall: The Spavin Group. 23 in defective elasticity unless specially posed, while in the horse the long axis of the limb describes great alternating angles, the scapulo-humeral opening backwards, the humero-radial forwards, and the phalanges extending obliquely downwards and forwards from the metacarpus. When a horse places its weight upon the end of the last phalanx, the smallest base of support seen in any mammal, the very narrowness of that support, combined with the angles in the limb and especially the obliquity of the pastern, serves to almost entirely prohibit lateral impact, and any violence - tends rather to decrease the angles and shorten the limb. As a result dislocation and strain are well-nigh unknown, and the lateral articular ligaments in the horse are comparatively small except in the scapulo-humeral articulation, where passive liga- ments are replaced by powerful muscles which permit of a con- siderable normal displacement of the articulation without injury. It thus occurs that lateral or median luxation in its ordinary meaning almost never takes place anywhere in the anterior limb of the horse whereas it is comparatively frequent in the arm of man, not an articulation escaping. The mechanism to prevent antero-posterior luxation in the horse is highly developed, the powerful biceps assumes the role of a great musculo-tendinous band to retain the scapulo-humeral articulation in front while the anconean group of muscles pre- vents the sufficient opening of the angle behind to admit of posterior luxation and at the same time the two muscles guard, in a reverse manner, the humero-radical articulation. Beyond these, the great flexor muscles and their powerful tendons serve as elastic supports upon which the articulations rest securely behind with little need for posterior ligaments and with the weight ever inclining backwards upon these tendons to such a degree that almost no provision is required against anterior dis- placement, or anterior strain. , In man, on the other hand, the great freedom of movement in every direction, including rotation, submits each and every joint to overtension of its ligaments. They may become strained or may rupture and luxation follow, or the ligaments may prove too resistant and the bones become fractured. Anatomically strains and luxatuions and fractures resulting therefrom should be common in man and very rare in the horse. Clinically we observe these quite commonly in the thoracic limb of man and abundant strains which do not end in luxation or fracture, but are ' 24 Williams, Fisher, and Udall: The Spavin Group. clearly diagnosable as strain by immediate pain in the part fol- lowed by rapid inflammation, which tends finally to subside after rest, with thickening and weakening of the ligaments, and with- out exostosis or ostitis. In the anterior limb of the horse, the guardianship of the great flexor tendons over the articulations is well shown by the frequent strain or rupture of these structures, whereas in man, ithe feebly developed corresponding parts rarely suffer injury, which is instead borne by the bones and articulations. Upon examining the pelvic limb we observe an equally pro- nounced contrast in anatomical arrangement as related to strain so far as it is borne by the joints and bones or by the great musculo-tendonous apparatus. - In man the femur continues the spinal column in an approx- imately direct line, while in the horse it is directed abruptly forwards upon a horizontal spinal column, forming an angle opening forward, at once reversed at the knee where the femur and tibia are on a direct line in man. The great angle of the tarsus opening forward in the horse is highly efficient in ward- ing off lateral strain, while in man it is lost by the tarsus coming in contact with the ground. The entire limb of man is practically direct from the hip to the ground, and supports above the up- right spinal column, so that any violence of movement falls directly upon an unyielding, erect column, the bones and liga- ments of which must suffer, while in the horse the great angles. of the limb effectively ward off strain and throw it from the bony column upon the powerful musculo-tendonous apparatus which receives the shock and records the consequences in strains and ruptures of the great flexor tendons. (In this comparison we view as a tendon the so-called suspensory ligament of the fetlock, which contains muscle fibers, represents an active muscle in man, and is described as a muscle in the horse by various anatomists, especially the Germans, and properly belongs with the great flexor tendons whose functions and injuries it shares.) We must therefore conclude that both anatomically and clinic- ally man is preéminently disposed to strains and their finality,. luxations, or fractures, while in the horse the impact of trans- mitted violence falls upon the musculo-tendonous apparatus. We rarely see a luxation or dislocation from a strain in the limb of a horse except the foot becomes caught in a tramway or similarly firm place. Without anatomical evidence of liability Williams, Fisher, and Udall: The Spavin Group. 25 of strain or clinical proof of its frequent occurrence, we are com- pelled to conclude that strain bears but a secondary part in the etiology of this group of affections. Concussion. Concussion is so closely related to strain, it is the sudden impact of one body against another in a manner which tends to crush the weaker of the opposing bodies, rather than to divide it by fracture or rupture, that we might define it as the same force acting in a different direction. The effect of — concussion depends largely upon the resiliency of the surface of contact and the facility by which it may glide away from the concussing force. The articular ends of the long bones and the entire short bones are cancellated and elastic and the angular direction at which the bones of the extremities meet in a horse, — as already described, admit of their ready recoil in obedience to concussion. The disease does not most frequently attack those bones most subject to concussion, nor at the points where concussion is apparently the greatest. We observe the navicular bone swing- ing in the hammock-like tendon more frequently seriously at- tacked than the adjoining pedal bone, which certainly receives by far the greater concussion; but more interesting is the fact that the plantar surface of the navicular bone is universally the portion most obviously affected, whereas if concussion caused it, the chief pathologic changes should be found on the dorsal sur- face which, so far as we know, always escapes. In ringbone con- cussion plays no very evident part. In horses with exceedingly oblique pasterns, the disease is probably as common as in those with upright pasterns and certainly more recalcitrant to all at- tempts at cure, yet the obliquity of the pastern obviates concus- sion and supplants it with strain on the tendons. In spavin it is difficult to see how there can be greater con- cussion between the lesser bones of the tarsus and the metatarsus than between the astragalus and tibia, yet the former constantly suffers and the latter only very rarely. Some have suggested that the anchylosis of spavin is a pro- cess of evolution tending ultimately to efface the latter joints, but the tendency is seen only in diseased animals which, if the con- tention were true, would tend to show that it is a pathologic evolution. Gonitis can ‘scarcely be regarded as the result of concussion as the parts usually affected are those most widely propped apart 3 ‘ 26 Williams, Fisher, and Udall: The Spavin Group. by means of the fibro-cartilaginous discs. Throughout the entire group, it cannot be well charged that concussion plays a funda- mentally essential réle in the causation of the malady. It is instructive also to study the frequency of this group of affections in those animals where concussion and strain are most common and violent compared with those whose environment protects them most completely from these injuries. Were we to single out the horse amongst all others which is most subject to strain and concussion, we would probably select the fire department animal, whose work is on a hard pavement, before a heavy load, starting suddenly at a run under the whip and continuing at high speed until reaching the destination, or stopping from exhaustion. This horse may split the hoofs, rup- ture the tendons, or break the bones, but is probably about the- freest horse ini existence from ringbone, spavin, and navicular disease. Or let us take the cow horse of the west, bearing a saddle of seventy-five pounds and a rider of two hundred pounds during a long and trying day, a large part of the time at a brisk gallop, over bank and coulee, badger holes and prairie dog towns, over stones and through morass, dodging an enraged animal, darting here and there in pursuit of fleeing stock and, when the lariat is thrown, the horse must suddenly stop to bring his quarry to the ground and then be keenly alert to hold it. Such animals break their legs or necks, but rarely suffer from ringbone, spavin, or navicular disease. We might enlarge further and it would be found that those animals put to hard, trying work, constant in character, are not the ones to suffer from these affections, though admittedly suffering much from strain, and concussion. On the other hand, we have seen foals less than six months old which had been born in a box stall and had never been allowed the pleasure of a frolic, to show four large ring- bones and two well-marked spavins. It is a well-known fact that horses used intermittently, or horses doing light delivery work, but kept all day long in the harness standing tied to a post, like peddler’s horses and delivery horses belonging to small concerns, suffer very seriously, as do also the cheaper class of private horses and children’s ponies, which are only occasionally used as opportunity or caprice of the owner may dictate. It is very common also in those pet horses which are driven very sparingly and infrequently or rarely. Again it is to be noted that horses suffering from severe Wiliams, Fisher, and Udall: The Spavin Group. 27 strain or violence to a limb do not as a rule develop this affection in the injured member, but while standing upon the other legs, develops the disease in them, or, perhaps more closely felated to this group than we have yet admitted, the well foot suffers in time from sinking of the os pedis, which Dollar translates in ‘his version of Mller as “ standing laminitis.” Regardless of the contention that the strain causes the ring- bone, navicular disease, spavin, or other similar ailment on the supporting limb, it certainly should be more likely to occur in the injured member as the result of the greater strain which caused the original disaster. FauLty SHorinc. Improper shoeing has been blamed for well-nigh all the ills to which horse is heir and has fairly won enough opprobrium. Its effect in inducing this malady should be viewed carefully. We all fully realize that careful shoeing, pathological shoeing as we sometimes term it, definitely alleviates some cases of ring- bone, spavin, or navicular disease, and we may well deduce therefrom that improper shoeing has a definite relation to the cause, but whether its influence is fundamental or contributory, perhaps we will not all agree. Since all stabled horses are shod and most horses affected with this disease are stabled, it is very easy to blame the shoeing, and since the feeling existing between the average practitioner and shoer is frequently not very cordial, it is easy to place the blame on the latter. We have no data to show that barefooted horses, when kept under the same conditions, suffer any less than those which are shod. We would not have it understood that we think shoeing exerts no influence, but that the relation is contributory or sec- ondary and we shall recur to this influence later. CoMPRESSION FROM TENDONS. The idea of Dieckerhoff that spavin is due to a tendo-vaginitis of the cunean division of the flexor metatarsi tendon is supported by the curative results fre- quently obtained by cunean tenotomy, but the deduction cannot be extended to most other members of the group. The argument is perhaps equally good in reference to navicular disease. But the influence of the compression of tendons is so limited in its scope that it cannot be relied upon as an essential etiological factor. We believe, however, and to that extent agree with Dieckerhoff, that it does play a very important secondary role in the two affections noted, and shall deal further with this question below. \ 28 Williams, Fisher, and Udall: The Spavin Group. CoNTRACTION OF THE Hoor. The contraction of the hoof has only been alleged to act in relation to one or, perhaps, two of the maladies, navicular disease and sidebones, and hence loses much of its interest to us in considering the etiology of the group. Even in the specified maladies the question is one of ani- mated’ controversy, some urging its causative importance, others denying it wholly and assigning it a position of effect instead. Certain it is that chronic navicular lameness is accompanied by contraction, but it is difficult to show that it causes the affection, if we look upon navicular disease as a separate malady. When considering navicular disease as one member of a great group, contraction and dryness of the hoof must be reckoned as a contributory or modifying cause rather than essential. Lavor. CONFINEMENT. The character of the labor or degree of confinement apparently exerts a profound influence upon the development of the affection. We have already referred to this in considering the influence of strain and concussion. In gen- eral, it may be stated as a rule that those animals are most free “~9m these affections which are either regularly worked, whether moderately or severely, or enjoy the constant freedom of the open range or pasture, and that those are most vulnerable which are closely confined and kept in enforced idleness, worked inter- mittently, or put at work where they are driven but a brief time each day and kept standing hitched in a vehicle during long hours. In the free clinic of the New York State Veterinary Col- lege, where many of these observations have been made, it is found that numerous cases occur during April, May, and June. The farm animals in this community have little or no work during the winter months, and are generally kept closely stabled without exercise, on a limited diet of oats and hay, and, soon after being put to work in the spring, develop lameness, due to some member or members of this group. How con- finement may act prejudicially we do not know, but the clinical evidence of its influence is strong. The horse is preéminently an animal of action, and any severe restriction tends to lower his power of resistance to disease. This group of affections is generally considered the special heritage of city horses, which are constantly subjected to stabling, shoeing, and working on hard streets Williams, Fisher, and Udall: The Spavin Group. 29 We have already pointed: out that shoeing cannot influence the whole group, but only a few members, and paved streets can scarcely occupy an essential place, or the disease could not be abundant in country places. In the vicinity of the New York State Veterinary College the disease among farm horses is so prevalent as to givé it the proportions of an enzodtic of serious import, but there are no paved roads to act as a causative factor. Ciimate. The effect of climate has not been well studied, but it is known that this group of affections have rather inter- esting geographical limitations, but whether this is due directly to the effect of the climate upon the horse, or whether it is rather indirect through the food and the necessity for stabling has not been definitely ascertained; but, so far as observed, its influence is indirect. The affection is most common in the eastern United States, and in the great cities of the middle states ; it is comparatively rare in the agricultural districts of the Mis- sissippi valley, and becomes more rare as the Rocky Mountains are approached, where over large areas it is practically unknown, to become more common again on the Pacific slope. Various explanations may be offered. The horse normally belongs to high, arid or semi-arid plateaus with dry soil and not very abundant vegetation of a high nutritive value and free from fungi, which conditions are attained in those regions where the disease is most rare. We must at the same time note that in these regions the horse enjoys the greatest liberty and is little confined in stables; it is, moreover, the newest part of our country. The senior contributor has noted an apparent increase of this malady in central Illinois as the country be- comes older and the soil and crops have undergone changes as the outcome of contintied cultivation. Foop.