vin.] THE MUSCLES. 327 



Echidna) exclusively arise from the external surface of the 

 scapula. 



The coraco-brachialis of man does not normally exhibit 

 the complexity of structure which it may exhibit in some 

 other Mammals. Thus, in addition to the part usually 

 developed in man (namely, that descending to about the 

 middle of the shaft of the humerus), we may have a shorter 

 part inserted above the tendon of the teres major and con- 

 nected with the capsular ligament (as in the Bonnet Monkey 

 and many other species), and a third part descending right 

 down to the internal condyloid ridge of the humerus, as in 

 the Echidna, in Lemur, Iguana (Fig. 296), and others. 



FIG. 294. MUSCLES OF INSIDE OF RIGHT ARM OF Iguana (seen in front), the 

 pectoralis and deltoid being cut short and reflected. 



B, biceps; EA, brachialis anticus ; CJS 1 and C2? 3 , coraco-brachialis; Z* 1 and 

 D 2 , deltoid; EH, muscles perhaps answering to the subclavius; IS, infra- 

 spinatus ; P, pectoralis ; SCM, stern o-cleido-mastoid ; T 1 ^, triceps. 



The biceps as it exists in man is a fair exponent of its 

 normal condition, at least in his class. This muscle, however, 

 may arise from but a single head, which may take origin 

 from the scapula only, as in the Pig, or from the coracoid 

 only, as in the Echidna and the Iguana. Its insertion may 

 take place both into the ulna and radius, as in the Pig, and the 

 two tendons of insertion may divide, allowing the brachialis 

 anticus to pass between them, as in the Chameleon. This 

 muscle may arise even from the sternum, as in the Frog. 



Brachialis anticus. This is rather short in man. It may 

 be divided into two parts, as in the Agouti. It may be more 

 or less confounded with the biceps, as in Iguana, Menopoma, 

 and Menobranchus. 



