THE UPPER EXTREMITY. 129 



tion of the deltoid is liable to fracture of the anatomi- 

 cal neck, which is intra-capsular, and to fracture of the 

 surgical neck, which is extra-capsular. In the former 

 there is little or no displacement due to muscular action ; 

 in the latter case the upper fragment is drawn up slightly 

 by the supra- and infra-spinatus, teres minor, and sub- 

 scapularis ; the lower fragment is drawn inwards by the 

 pectoralis major, latissimus dorsi, and teres major, 

 whilst the deltoid draws it obliquely from the side of 

 the body. 



In cases of fracture of the anatomical neck, with sep- 

 aration, it may necrose, owing to there being no means 

 of vascular supply to the fragment, and if not, it may 

 be inferred that impaction has occurred. At any rate, 

 whatever amount of repair does take place is due to the 

 lower portion of the shaft of the bone. In impacted 

 fracture the axis of the bone is obviously altered, and 

 there is a slight cavity beneath the acromion, owing to 

 shortening. The upper articular extremity unites with 

 the shaft at about the twentieth year. 



The upper epiphysis is sometimes separated in infants, 

 in consequence of the carelessness of nurses in lifting 

 them suddenly up by the arm, giving rise to most se- 

 rious mischief. 



The landmarks already described in the superficial 

 examination of the shoulder are of the greatest impor- 

 tance in the performance of the operations of amputation 

 at the shoulder-joint, and of excision of the head of the 

 humerus. A great number of methods are described in 

 works on surgery for the accomplishment of the disar- 

 ticulation, but it will suffice to mention two only viz., 

 that of the operation by lateral flaps, and the oval 

 method, but only as far as anatomy bears upon the 



