ANATOMY OF A MONODACTYLOUS FOETUS 397 

 BRACHIAL MUSCLES 



Coracobrachialis (fig. 8, C) 



Origin. From the coracoid process, and capsule of the 

 shoulder joint, by a common tendon with the short head of the 

 biceps. The capsular origin is uncommon. The muscle in its 

 upper part receives fibers from the pectoralis minor as mentioned 

 above. 



Insertion. Into the medial side of the humerus from the 

 level of the lesser tuberosity klmost down to the medial epi- 

 condyle. What are here present are thus all three divisions of 

 the muscle, namely, superior, middle and inferior portions. 



The superior portion here exhibited is rarely found in man 

 though normal to some of the lower animals. The coraco- 

 brachialis superior, when present, inserts into the lesser tuber- 

 osity, surgical neck, and medial bicipital ridge of the humerus, 

 also frequently into the capsule of the shoulder joint. It occurs 

 only very rarely in the Anthropoidea but as a normal structure 

 in the Quadrumana. It is also present in the elephant, giraffe, 

 bear, cat, hyena, opossum. Echidna and several other animals. 



The coracobrachialis medius is inserted into the middle portion 

 of the humerus and forms the main mass of the normal human 

 muscle, the remainder being constituted of the upper part of the 

 coracobrachialis inferior. The medius is the only portion of the 

 coracobrachialis present in the aye-aye, the bat, and the sloth, 

 while it is absent in the kangaroo, otter, and seal. 



The coracobrachialis inferior has an extremely variable inser- 

 tion, extending in different cases from an attachment a couple of 

 centimeters long on the shaft of the humerus below the medius, 

 to an insertion on the inner edge of the whole lower half of the 

 shaft of the bone and the inner epicondyle. In the latter case 

 it bridges the supracondylar foramen in animals where this is 

 present and so is perforated by the median nerve and brachial 

 artery. This muscle is found in the cetacea, the hedgehog, the 

 bear, great anteater and others. The inferior portion is much 

 more developed here than is normal in man, but similar de- 

 velopment has been frequently found before. 



