MUSCLES OF THE ARM. 417 



arm. It arises by two heads. The first, called the long, is a 

 round tendon which comes from the superior extremity of the 

 glenoid cavity of the scapula, passes through the shoulder joint 

 and through the groove of the os humeri ; the second head arises 

 tendinous from the extremity of the coracoid process of the sca- 

 pula, in company with the coraco-brachialis muscle. The fleshy 

 bellies in which these tendons terminate, unite with each other, 

 several inches below the shoulder joint, to form a common mus- 

 cle. At first they are only connected by loose cellular sub- 

 stance ; but, about half-way down the arm, they are insepara- 

 bly united. 



The biceps terminates below in a flattened oval tendon, which 

 passes in front of the elbow joint, to be inserted into the poste- 

 rior rough part of the tubercle of the radius. A bursa mucosa 

 is placed between the tendon and the front of the tubercle, the 

 surface of the latter being covered with cartilage. From the 

 ulnar side of this tendon proceeds the aponeurosis running into 

 that of the fore arm. 



The relative position of the biceps is as follows: Its long 

 head is first within the cavity of the capsular ligament, and then 

 between the tendons of the latissimus dorsi and pectoralis ma- 

 jor, where it is bound down by strong ligamentous fibres. The 

 tendon below is superficial, and may be easily felt by flexing 

 the fore-arm, but its insertion dips down between the pronator 

 teres and supinator radii longus. 



This muscle flexes the fore-arm.* 



The Coraco-Brachialis, 



Is situated on the upper internal side of the arm, at the inner 

 edge of the short head of the biceps muscle, with which it is 

 connected for three or four inches. It arises tendinous and 

 fleshy from the middle facet of the point of the coracoid pro- 



* Varieties. Sometimes the division of the muscle is continued to the elbow; 

 sometimes there is a third head, coming either from the internal face of the os 

 humeri, or from the brachialis internus; very rarely, the number of heads^has 

 been multiplied to five, thereby making a close approximation to the arrangement 

 in birds. This muscle is very liable to anomalies. 



