138 CONTRIBUTIONS TO ZOOLOGICAL PATHOLOGY. 
employed by them in obtaining their means of existence, a neces- 
sarily increased activity must take place in this as well as in all 
the other joints of the body, and thus preventing the fuller deve- 
lopment of that which is even malformed at first. 
On reviewing the appearances seen in the above case, and com- 
paring them with those that may be produced by disease (if any 
doubts could arise as to these appearances having been the result 
of domestication, and not produced by a congenital defect*), the 
only proximate conditions that can be placed in apposition to 
them, are those seen as the effects of interstitial absorption of the 
head and neck of the thigh-bone, and chronic rheumatic arthritis 
of the soft tissues of the joint. Though both these morbid actions 
are now placed under the same general definition, and viewed as 
the result of the same morbid cause, I shall, for the sake of com- 
parison, consider the two appearances individually, inasmuch as 
interstitial absorption of the osseous paste, and a corresponding 
change in the length and angle of the neck and the articular sur- 
face of the thigh-bone may occur, without much, if any, disease 
being co-existent in the peripheral tissues. 
This form of disease in the osseous structure of the joint was 
particularly described by Benj. Bell; and as he gives a most per- 
fect and lucid description of it, I shall transcribe it in his own 
words. 
“In the advanced stages of the disease,” says he, “there is 
something resembling a yielding or bending of the neck of the 
bone, so that the inferior edge of the corona of the bone approaches 
the trochanter minor. This effect does not proceed from any soft- 
ening or alteration in the intimate structure of the bone, but arises 
in consequence of the absorption and disappearance of a portion 
of its entire substance. On a cursory examination, it looks as if 
the head of the bone were forced downwards by the action of some 
great pressure ; and in some cases the interstitial absorption pro- 
ceeds so far, that the head of the thigh-bone rests upon the upper 
part of the trochanter minor, which, in some instances, becomes 
hollowed out for its reception. In some rare cases, combined with 
the shortening of the cervix femoris, there is also a flattening of 
the head of the bone, and the formation of a deep groove around 
the lower edge of the corona, and occasionally more than two- 
thirds of the neck of the bone disappears, so that the head of the 
bone becomes forced in the direction of its axis towards the base 
of the trochanter majort.” 
I have seen several well-marked cases of this form of the disease 
* It is well known, that animals which have been domesticated from a 
state of nature suffer most changes in their osseous system. 
f Bell on Diseases of Bone, p. 94 et seq. 
