The shaft of the humerus, protected as it is by heavy muscles, is not frequently fractured; and fractures of its less protected parts, as for example, the head, are complicated in such manner that resultant arthritis soon constitutes the more serious condition. As a result of falls on frozen ground, kicks or any other form of heavy contusion, the humerus is occasionally broken. It is rarely fractured otherwise. Because of the force of contusions usually required to effect humeral fracture, the manner in which the bone is broken, with respect to direction, is variable. Often oblique fractures exist and occasionally there occurs multiple fracture. In addition to the ordinarily serious nature of the fracture itself, there is always much injury done the adjoining structures. Symptomatology.--Mixed lameness and manifestation of severe pain characterize this affection. Considerable swelling which increases, in some cases for a week or more, is to be observed. Crepitation is readily detected, if pain and swelling is not too great to prevent passive movement of the member. Where intense pain is not manifested, because of manipulation, one may abduct the extremity and thereby occasion distinct crepitation; but when it is possible to recognize crepitation by holding the hand in contact with the olecranon while the animal is made to walk, this method is to be preferred, if the subject can move without serious difficulty. The pathognomonic symptom here is recognition of crepitation, but this may be very difficult to recognize in fracture of condyles, and in such instances, a careful examination is necessary. Gentle manipulation in a manner that pain is not aggravated will tend to inspire confidence on the part of the subject and relaxation of muscles will enable the operator to detect crepitation. Course and Prognosis.--Because of the direction of the long axis of the humerus, with relation to the bony column of the extremity, it is obvious that any lateral movement of the leg tends to rotate the shaft of this bone. In fractures of the shaft of the humerus, then, it is apparent that immobilization is very difficult if at all possible.