344 A MANUAL OF ANATOMY 



is remarkable for its length, descends, along with the ulnar nerve, 

 to enter the internal head low down, this branch being known as 

 the tdnar collateral nerve (Krause). The internal cutaneous branch 

 usually arises in common with one of the muscular branches, and 

 is distributed to the integument of the back of the arm, reaching 

 nearly as low as the back of the elbow. 



Posterior Branches. — ^These arise behind the humerus, and are 

 distributed to the external and internal heads of the muscle and 

 to the anconeus, the nerve to the latter, which is long and slender, 

 descending in the internal head. 



External Branches. — These arise on the outer side of the 

 humerus, and are cutaneous, muscular, and articular. The upper 

 and lower external cutaneous nerves have been already described. 

 The muscular branches are distributed to the brachio-radialis, 

 extensor carpi radialis longior, and brachialis anticus, the latter 

 branch being a small twig. The articular branches, one or two in 

 number, are distributed to the elbow- joint. 



THE SHOULDER-JOINT. 



The shoulder-joint belongs to the class diartkrosis, and to the 

 subdivision enarthrosis (ball-and-socket). The articuW surfaces 

 are the glenoid cavity of the scapula and the head of the humerus ; 

 and the ligaments are the capsular, coraco-humeral, gleno-humeral, 

 and glenoid. 



The capsular ligament is attached to the scapula around the 

 margin of the glenoid cavity close to the glenoid ligament, with 

 which many of its fibres are connected. Superiorly it extends to 

 the root of the coracoid process, and inferiorly it is related to the 

 long head of the triceps. At the himienis it is attached to the 

 anatomical neck, its fibres descending for a little on the inferior 

 aspect. The ligament is very loose, so that, when the muscles in 

 contact with it have been divided, the head of the humerus drops 

 away from the glenoid cavity for over an inch. The ligament 

 presents two openings. One, called the foramen ovale, is situated 

 on its anterior aspect, behind the upper border of the subscapular is. 

 Through this opening a protrusion of the synovial membrane of 

 the joint takes place beneath the upper border of the subscapu- 

 laris, where it forms the subscapular bursa. The other opening is 

 placed between the great and small tuberosities of the humerus at 

 the commencement of the bicipital groove, and it allows the long | 

 tendon of the biceps, with its synovial investment, to leave the 

 interior of the joint, beneath the transverse humeral ligament. 

 There is sometimes a third opening of small size on the posterior 

 aspect of the capsule, which allows the synovial membrane io 

 protrude and form a bursa beneath the infraspinatus. 



The coraco-humeral ligament is a strong band which extends ; 



