582 



HUMAN ANATOMY. 



that it is continuous above with the neck and inferiorly with the axilla. The latter 

 space is shut in below by the continuation of the axillary fascia from the lower bor- 

 der of the pectoralis major backward to the latissimus dorsi, outward to the deep 

 fascia of the arm, and inward to the deep fascia of the thorax. 



Abscess or effusion of blood, as its progress in all these directions is resisted, 

 may therefore point in the neck, following the vessels and the trunks of the plexus 

 up from the axilla through the deep infraclavicular triangle, to make its appearance 



above the clavicle. 



The skin over the fascia at the base of the axilla is thin and richly supplied 

 with hair-follicles and with sebaceous and sudoriparous glands ; hence superficial 

 infections are frequent and secondary glandular abscesses are common. The con- 

 nective tissue of the axillary space is loose and abundant, permitting of free motion 

 of the arm, but also favoring the occurrence of large collections of blood or of pus. 



Fig. 565. 



Fig. 566. 



1^ 



Clavicle 



Acromion, 

 process 



Coracoid 

 process 



Head of 



humerus 



Shoulder of subject in which subcoracoid lux- 

 ation has been produced, showing characteristic 

 deformity. 



Acromion 

 Coracoid-it.^ 



Glenoid — sL. 



cavity- 

 Head of 



humerus 



Showing relation of bones in preceding subcoracoid 

 luxation. 



The fascia over the scapular muscles — supraspinous and infraspinous fascia — 

 has already been described in reference to caries, necrosis, and abscess (pages 



255, 279). 



Dislocation of the Shonlder-Joint. — The circumstances that favor or resist dislo- 

 ration of the shoulder-joint have been enumerated (pages 27S, 279), but the ana- 

 tomical symptoms of that lesion may now be considered with especial reference to 

 the muscles involved. Shoulder dislocation is either subglenoid or subcoracoid in 

 the vast majority of cases, the former being almost invariably the primary form, for 

 reasons previously given (page 278). 



A luxation, subglenoid primarily, usually becomes subcoracoid from the con- 

 tinuance of the force producing it, aided strongly by the pectoralis major ; hence 

 the subcoracoid is the most common. The subclavicular, in which the head passes 

 farther inward and lies on the second and third ribs beneath the pectoralis major, 



