SHOULDER, ARM, FOREARM, AND HAND. 185 



under the anterior annular ligament, and between the two heads of the flexor brevis 

 pollicis, to the base of the distal phalanx of the thumb, where it is tendinously 

 inserted. 



You are to study the radial oblique line, and let your dissections show 

 the following points : 



1. It terminates above in the bicipital tuberosity, and into this tuberosity is 

 inserted the tendon of the biceps muscle. 



2. It terminates below in a round depression, and into this is inserted the 

 pronator radii teres muscle. (Fig. 128.) 



3. It has three lips : an outer, into which is inserted the supinator brevis 

 muscle ; a middle lip, that gives origin to the radial head of the flexor sublimis 

 digitorum, and location to the nutrient foramen of the radius ; an inner lip, that 

 gives origin to the flexor longus pollicis. (Fig. 124.) 



THE FOREARM FLEXORS. 



In the order of their strength they are as follows : 



1 . The musculus biceps cubiti or biceps muscle. 



2. The musculus bracliio-radialis or supinator longus muscle. 



3. The musculus bracJdalis anticus very broad and fleshy. 

 Dissect and study the biceps with reference to : 



1. Its origin by a coracoid or short, and a scapular or long head. 



2. Its insertion by a tendon and by an aponeurosis. 



3. Its fusiform belly and the rule for the nerve-supply of muscles. 



4. Its inferior, external, and internal relations. 



5. Its synergists and antagonists, and nerve-supply. 



6. Its limiting intermuscular fasciae. 



7. Its fibrous arch and the rule for fibrous arches. 



The biceps (Fig. 126) you have found inserted aponeurotically, by the bicip- 

 ital or semilunar fascia, into the deep fascia, over the pronator radii teres muscle. 

 It is tendinously inserted into the bicipital tuberosity of the radius. It arises 

 by two heads, called long and short. The long head arises from the bicipital 

 tubercle, above the glenoid cavity of the scapula; it passes under the transverse 

 humeral ligament of the shoulder, between the greater and lesser tuberosities of 

 the humerus, in the bicipital groove. The short head you will find arising from 

 the apex of the coracoid process of the scapula, with the coraco-brachial muscle. 

 These two heads of the biceps are connected by a fibrous arch. See rule for 

 fibrous arches in the introductory chapter. The biceps muscle rests on the brachi- 

 alis anticus muscle. Under the biceps muscle you will find the musculo-cuta- 

 neous nerve which supplies it and also the brachialis anticus, coraco-brachial, 

 and supinator longus muscles. Externally are the deltoid and triceps and 

 pectoralis major. Internally are the triceps, the latissimus dorsi, teres major, and 

 coraco-brachial muscles. Lift the biceps from its bed, pull the same outward, 

 and you will expose the brachialis anticus muscle below. In the groove, between 

 the triceps and the inner part of the biceps, are to be found the large branches of 

 the brachial plexus and the brachial artery and its venae comites. 



The brachio-radialis or supinator longus muscle (Fig. 128) arises from the 

 upper two-thirds of the outer condylar ridge of the humerus. (Fig. 129.) It is 

 inserted into the base of the radial styloid process. It has the double function of 

 flexion and supination. Trace to it nerves from the flexor trunk, the musculo- 

 cutaneous, and from the extensor trunk, the musculo-spiral. 



The brachialis anticus (Fig. 127) arises from the outer and inner surfaces of 

 the humerus, limited above by the insertion of the deltoid and coraco-brachial 

 muscles. (Fig. 129.) Its insertion you have already seen into the coracoid pro- 



