720 
DISEASES OF THE HOCK. 
An unprejudiced examination of the foregoing views can only lead us 
to the conclusion that to regard spavin as invariably originating in one 
of the regions named* h<?., to consider it as a fixed and invariable disease* 
is an untenable position. The variations in the anatomical changes 
discovered by different observers are due less to the stage at which the 
disease has arrived than to fundamental differences in its nature. 
Depending on whether the disease has arisen from injury to the bone or 
to the ligaments, the anatomical changes will vary. Only on this 
hypothesis can we explain why in one case a large exostosis is accom¬ 
panied by spurious anchylosis, and in another a scarcely visible bony 
enlaigement is found along with true anchylosis between the cuneiform 
bones or between the cuneiform and the metatarsus. For this reason, 
T rick, whilst keeping an open mind as to the essential nature of spavin, 
declares that the most varying forms of chronic disease of the inner 
surface of the hock may produce the clinical appearances which, in 
practice, we recognise as “ spavin.” Anatomically, spavin may be 
divided into various forms which, however, may all be regarded as having 
one point in common, viz., that they eventually lead to deformity of the 
affected joint, and may, therefore, rightly be designated as Arthritis 
chronica deformans. In a word, “ spavin is a collective clinical term 
covering a number of extremely diversified anatomical changes in the hock. 
Pathological anatomy. Anatomical examination reveals :— 
(1) Changes in the articular cartilage of the cuneiform, and of the 
upper part of the metatarsus, sometimes of the scaphoid, and other 
bones of the hock. Changes in the cartilage, abrasions, ulceration, 
and, at the borders of the articular surfaces, rugged, uneven swellings, 
produced by thickening of the cartilage, which later becomes ossified, 
can all be detected by the naked eye. Microscopically, the intercellular 
substance is seen to be fibrillated, and the cartilage cells to be under- 
gomg multiplication, piocesses peculiar to arthritis chronica deformans. 
(2) The affected bones show deposits termed osteophytes, which 
sometimes stait fiom the ossified cartilaginous growth, sometimes result 
from inflammation attacking the periosteum of the bones named. Gotti 
and Lberlein state that the bone shows rarefying and condensing ostitis. 
lliis local growth of bone is in fact the so-called spavin. It is 
usually only a secondary symptom due to inflammation extending from 
the articular surface to the periosteum. 
(8) Changes in the ligaments and synovial membrane. Doth the 
villi and boideis of the synovial membrane seem thickened and vascular. 
Sometimes the secretion of synovia is excessive. The ligaments of the 
joint, and the connective tissue surrounding it, are also thickened. 
(4) In advanced stages of the disease, the smaller joints may be 
obliterated, especially those between the scaphoid and cuneiform bones, 
