222 



APPLIED ANATOMY. [Chap. XL 



3. Subspiiious. The head usually rests on 

 the posterior surface of the neck of the scapula, the 

 groove of the anatomical neck of the humerus corre- 

 sponding to the posterior lip of the glenoid fossa. 

 The head is thus placed beneath th.e acromion ; but it 



may be displaced still 

 farther back, and may 

 rest on the dorsum 

 scapula 1 , and beneath 

 the scapula i 1 spine 

 (Fig. 20). The sub- 

 scapularis tendon is 

 drawn right across the 

 glenoid fossa, and is 



/ff^m fi/i/: / often torn from its 



jjji mi n (/ / attachment. The head 

 f Im mli tii I/ / pushes back the hinder 



/ I ill!., Ytf p art of the deltoid ' the 



infraspinatus, and teres 

 minor muscles. These 

 latter cover the bone, 

 and are stretched over 

 it. The supraspinatus 



Fig. 20. Sub; 



>ST> 

 11. 



inous Dislocation of 

 .irnerus. 



is tense, as is also the 

 biceps, while the teres 



major and latissimus dorsi are relaxed. The great 

 pectoral is rendered unduly tense, and this sei-ves 

 in part to explain the rotation inwards of tire 

 huraerus, and the adduction forwards, that ai'e usually 

 observed, those movements being more or less un- 

 opposed. The circumflex nerve is often torn. 



In reducing dislocations, especially such as are of 

 long standing, serious damage may be inflicted on the 

 axillary structures. The axillaiy artery suffers most 

 frequently, the vein rarely, and the nerves still less 

 often. The artery, being placed externally, is apt to 

 contract adhesions to the soft parts covering the head 



