78 TOPOGRAPHIC AND APPLIED ANATOMY. 



FIG. 31. A model of the shoulder-joint and its bursae. The two bursae communicating with the articular cavity 

 as well as the joint itself are colored blue. The non-communicating subdeltoid bursa is represented in red. (From 

 a Berlin model.) 



FIG. 32. A cross-section through the middle of the arm (hardened in formalin). 



In the internal bicipital groove, about at the junction of the lower with the middle third of 

 the arm, there is an opening in the deep fascia, which is known as the hiatus basilicus, for the 

 passage of the basilic vein and the internal cutaneous nerve. In the external bicipital groove the 

 cephalic vein runs upon the deep fascia (see page 73). 



The brachial artery runs beneath the deep fascia in the internal bicipital groove; it is ac- 

 companied by two veins, the inner of which receives the basilic vein. Higher up, the venae comites 

 unite to form a single vein, either before reaching the axilla or, more rarely, after entering into 

 this region. Disregarding the muscular branches, of which the bicipital is particularly large, the 

 main branches of the brachial are: 



1. The superior projunda artery, which accompanies the musculospiral nerve about the 

 posterior surface of the humerus, in the musculospiral groove, between the outer and inner heads 

 of the triceps muscle. It ends at the outer side of the humerus, where it is accompanied by a 

 cutaneous branch of the musculospiral nerve, and descends behind the external intermuscular 

 septum to reach the anastomotic arch above the olecranon (rete articulare cubiti). The poste- 

 rior articular branch of this vessel runs downward in the posterior portion of the arm in the sub- 

 stance of the inner head of the triceps muscle. 



2. The inferior projunda artery, usually a long vessel, which accompanies the ulnar nerve 

 to the olecranon, where it empties into the rete cubiti. 



3. The anastomotica magna artery, which arises near the division of the brachial in the region 

 of the elbow. It runs transversely inward across the brachialis anticus muscle and passes pos- 

 teriorly to the rete cubiti. 



The median nerve is the most superficial of the three chief nerves in the upper arm. At 

 first the nerve lies to the outer side of the brachial artery, it then passes in front of the vessel, and, 

 while still above the elbow, takes a position to the inner side of the artery. The nerve con- 

 sequently crosses the artery, and is to be felt lying upon the vessel, if. the panniculus adiposus is 

 not too well marked. The nerve is often situated beneath the artery, particularly in those cases 

 of so-called high division of the brachial in which the artery divides in the upper arm into two 

 parallel branches, one of which usually runs over and the other under the nerve. If the artery 

 first exposed is comparatively small, and if it lies upon the median nerve, a search should always 

 be made for a second artery. The median nerve gives off no branches in the upper arm. 



The ulnar, the second great nerve of the arm, lies internal to the artery, but gradually becomes 

 more distant from the vessel. It pierces the internal intermuscular septum at the lower third 

 of the arm and reaches the space between the internal condyle and the olecranon. The ulnar 

 nerve also gives off no branches in the upper arm. 



The musculospiral, the motor nerve of the extensor muscles, is at first behind the artery. 

 It enters the musculospiral groove, running upon the surface of the humerus between the outer and 

 inner heads of the triceps muscle, and at the lower part of the arm passes into the region of the 

 elbow between the supinator longus and brachialis anticus muscles. As the nerve lies directly 



