THE HUMERUS 45 



The inferior extremity of the inner condyle is roughened for the 

 attachment of the tendon of origin of the flexors of the digit, while that 

 of the outer condyle is similarly roughened, and gives origin to the 

 tendon of the flexor metacarpi externus. From the sharp anterior edge of 

 this condyle the extensor metacarpi magnus arises, and inferiorly to this 

 the extensor pedis arises from a pit which is placed to the outer side of 

 the coronoid fossa. 



The interior surface presents an articular area which enters into the 

 formation of the elbow-joint, and which is continued upwards on the 

 posterior aspect of the bone into the olecranon fossa. 



The nutrient foramen is placed in the inferior third on the inner 

 aspect ot the shaft of the bone, the vessel of supply being derived from 

 the brachial artery usually, but occasionally from its ulnar branch. 



In addition to the three usual centres for the ossification of the shaft 

 and epiphyses, this bone has three additional centres, one for the external 

 tuberosity and one for each of the two condyles. 



In the horse, fractures of the humerus are uncommon, since in this 

 animal the bone is comparatively short and extremely massive. More- 

 over, its position ensures for it a considerable degree of protection. 

 Portions of the outer tuberosity may be broken off as the result of a 

 severe blow. On the outer aspect of the bone the part most liable to 

 injury is the deltoid tubercle, since it stands out most prominently. 



Sumner had a peculiar case of fractured humerus in a heavy draught 

 horse, in which the bone was split through the articular head in a 

 vertical manner, the fractured portion including the deltoid tubercle and 

 ridge, the external tuberosity, and part of the articular head. Notwith- 

 standing the enormous swelling of the part, by palpation the deltoid 

 tubercle could be readily displaced. The animal was placed in slings for 

 ten weeks, and did so well that he was able to walk home [three miles] 

 without much difficulty. A recurrence of the fracture occurred through 

 the animal getting cast in the stall, and the patient was slaughtered. 



Fracture of the shaft of the humerus occurs as the result ot a 



