SESAMOID IT IS. 
631 
Upon laying open the principal sesamoidal joint, which 
articulates with the metacarpal bone, a considerable portion 
of the articular surface was absent, this being lost either by 
attrition or absorption. 
The disorganization was principally confined to the arti- 
cular cartilage belonging to the inner sesamoid bone, which 
had the small exostosis attached to it, in conjunction with 
the corresponding articulating condyle of the metacarpal; 
this extremity of the bone being completely denuded of its 
cartilage. 
Second Case , — A weight-carrying hunter of repute, slightly 
lame of his near fore leg. The projecting tumour in this 
instance was situated upon the outer ankle, and was more 
than double the size of that in the foregoing case, solid as 
bone, and situated exactly in the sesamoidal region, but 
surrounded by chronic ligamentous enlargement of the 
outside of the fetlock joint generally. The principal sus- 
pensory ligament and flexor tendons were in their normal 
condition. 
Dissection proved it to be the fac-simile of a bone- 
spavin upon the external surface of the outer sesamoid bone : 
an excrescence of solid bone, which was surrounded with 
many layers of condensed cellular tissue and thickened 
ligaments, especially the outer branch of the suspensory, a 
portion of which was completely embedded in the osseous 
protuberance. 
Upon exposing to view the extensive articular surfaces in 
contiguity with the diseased sesamoid bone, they were found 
quite intact , there being no abrasion of any portion of the 
synovial membrane ; neither was it discoloured ; so that the 
delicate structure of the interior of this complex joint appears 
to have escaped the invasion of disease, although morbid 
action must have prevailed in its very walls for a lengthened 
period. 
Remarks upon the above Cases. — These cases have 
been seized upon with avidity, because each is a type of the 
most important division of the subject : viz., the one sesa- 
moiditis within the joint, and the other sesamoiditis external 
to the joint. 
An attempt at the elucidation of the several varieties of this 
concealed unsoundness is a task which I have set myself. It 
may appear strange, but it is not the less true, that its clas- 
sification, or subdivision, will claim no inconsiderable space 
in all future dissertations upon veterinary pathological 
anatomy. 
