SHOULDER AND ARM. 



the distal extremities of the four inner metacarpals ; it is com- 

 posed of three sets of transverse fibres placed in front of the 

 three inner interosseous spaces. [288] 



Interphalangeal Joints. These are ginglymus diarthroses. 

 They resemble the metacarpo-phalangeal joints, each having a 

 capsule with palmar and lateral cord-like ligaments, and a 

 synovial membrane. The extensor tendons are their chief sup- 

 port dorsally, as in the metacarpo-phalangeal joints. [288] 



SHOULDER AND ARM. 



FASCIA. 



Fascia. Axillary Region. The pectoral deep fascia invests 

 the Pectoralis major and, at its outer border, becomes thickened 

 and forms the floor of the axilla (axillary fascia) ; thence it is 

 continued posteriorly onto the posterior fold of the axilla, and 

 externally to join the deep fascia of the arm. A deeper stratum 

 (costo-coracoid membrane') descends from the under surface of 

 the clavicle in two layers which enclose the Subclavius and 

 then unite in one layer; this splits again to enclose the Pec- 

 toralis minor, then unites and passes under the axillary floor to 

 join the fascia over the Biceps and Coraco-brachialis. The part 

 extending from the first costal cartilage to the coracoid process 

 is thickened (costo-coracoid ligament). [321] 



Shoulder. The deep fascia is attached to the clavicle and 

 the acromion process and spine of the scapula. [327] 



Arm. The deep fascia is attached to the condyles and ole- 

 cranon process. Two processes run inward from it to the su- 

 pracondyloid ridges; the stronger (internal intermuscular 

 septum) lies between the Triceps and Brachialis anticus and 

 extends upward to the insertion of the Coraco-brachialis; the 

 weaker (external intermuscular septum) lies between the Tri- 

 ceps and the Brachialis anticus and Brachio-radialis, and ex- 

 tends upward to the insertion of the Deltoid. [332] 



[157] 



