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. It 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~ 
