264 OPERATIONS ON BONES. 



peculiar snapping sound, audible and significant, as well as a 

 visible return of the surface to its normal symmetry. 



Special Dislocations. — WMLe all the articulations of the body 

 are liable to this form of injury, there are three in the large animals 

 which may claim a special consideration, viz: 



The Shoulder Joint. — We mention this displacement without 

 intending to imply the practicability of any ordinary attempt at 

 treatment, which is usually unsuccessful, the animal whose mishap 

 it has been to become a victim to it being disabled for life. The 

 superior head of the arm bone, as it is received into the lower 

 cavity of the shoulder blade, is so situated as to be liable to be 

 forced out of place in foui- directions. It may escape from its 

 socket, according to the manner in which the violence affects 

 it, outward, inward, backward, or forward, and the deformity 

 which results and the effects which follow will correspondingly 

 differ. We have said that treatment is generally unsuccessful. 

 It may be added that the difficulties which interpose in the way 

 of reduction are nearly insurmountable, and that the application 

 of means for the retention of the parts after reduction would be 

 next to impossible. The prognosis is sufficiently grave from any 

 point of view for the luckless animal with a dislocated shoulder. 

 The Hip Joint. — This joint partakes very much of the char- 

 acteristics of the scapulo-humeral articulation, but is more strongly 

 buUt. The head of the thigh bone is more separated, or promi- 

 nent and rounder in form, and the cup-Uke cavity or socket into 

 which it fits is much deeper, forming together a deep, true baU- 

 and-socket joint, which is, moreover, re-enforced by two strong 

 cords of fimicular ligaments, which unite them together. It wiQ 

 be easily comprehended, from this hint of the anatomy of the re- 

 gion, that a luxation of the hip joint must be an accident of com- 

 paratively rare occurrence. And yet cases are recorded in which 

 the head of the bone has been affirmed to slip out of its cavity 

 and assume various positions, inward, outward, forward, and back- 

 ward. 



The indications of treatment are those of all cases of dislocation. 

 When the reduction is accomplished the surgeon will be apprised 

 of the fact by the peculiar snapping sound usually heard on such 

 occasions. 



Pseudo luxations of the Patella. — This is not a true disloca- 

 tion. The stifle bone is so peculiarly articulated vsdth the thigh 



