CONTRIBUTIONS TO ZOOLOGICAL PATHOLOGY. 139 
in elderly people, and that, too, without much change in the con- 
dition or structure of the soft tissues. But in all these cases, 
though the head and neck of the thigh-bone had become almost 
sessile on the trochanters, yet, in all of them, the osseous me- 
chanism of the joint was perfect, the head of the bone, though 
small, was strictly confined to the cotyloid cavity, and the inter- 
articular ligament was entire. This latter circumstance, however, 
is not a necessary condition of structure ; for, as I shall imme- 
diately state, it has been found entirely destroyed in that form of 
the disease which involves more especially the softer structures. 
In all these cases that I have referred to, the elementary type of 
formation of the normal condition was always found in the sessile 
neck and head of the bone, on its being sawn through in its long 
axis, and there was not the slightest appearance in any of them 
that could positively be placed in apposition with the appearances 
seen in this case of malformation. 
The other form of morbid change above referred to, and in which 
the softer tissues are especially involved, has been carefully in- 
vestigated by Dr. Adams, of Dublin*. “ The fibrous capsule of 
the joint,” says he, “ is greatly thickened, the cotyloid ligament 
is either ossified or absorbed, and that ligament which completes 
the notch in the natural state is usually converted into bone. 
When the disease has been fully established, the ligamentum 
teres is altogether removed, the synovial fluid is deficient in 
quantity, and the cartilage is removed from the bottom of the 
acetabulum and the upper surface of the head of the femur ; and 
if any vestige of the synovial membrane remain, it is in a highly 
vascular condition. The acetabulum is generally much larger 
and deeper than natural, and forms a circular cup, often two inches 
deep, with a complete level brim, which is sometimes so much 
narrowed, as to render the extraction of the head of the femur 
difficult. 
“ This is the most frequent abnormal appearance that the ace- 
tabulum presents, though it is sometimes increased in size and 
very shallow, and of an oval form ; and when we examine the 
bottom of it, we find it widened, and not any trace of Haversian 
gland is left. The interior of the cavity presents a worn and po- 
rous appearance, the cartilage and compact stratum of bone which 
the cartilage normally covers is removed, and in some places, 
where the pressure and friction from the head of the femur have 
been greatest, instead of a rough, and worn, porous appearance, 
resulting from the exposure of the cells of the bone, a dense enamel 
* Vide Cyclopedia of Anatomy and Physiology, loc. cit. 
