MUSCULAR SYSTEM 113 



this point the muscle runs perpendicularly along the triceps 

 (radiating out into the surrounding fasciae) .to the condylus 

 internus humeri, into which it is inserted. This muscle is 

 present in all Anthropoids, and is either directly inserted into 

 the olecranon or contributes to the triceps. 



Near the sternal line the so-called " sternalis " muscle is 

 sometimes found. This is a small bundle, which varies in 

 form and in the direction of its fibres, lying ventrad of the 

 pectoralis major. It may either be bilaterally symmetrical or 

 present only on one side. In the former case, the two muscles 

 I may cross one another and be continued direct into the sterno- 

 'cleido-mastoid. 



[Considerable controversy has from time to time arisen con- 

 cerning this sternalis. It occurs in some 3 to 5 per cent of 

 subjects, and is invariably innervated by the anterior thoracic 

 or intercostal nerves. While it has by some been referred to 

 a possible origin from the pectoralis major, the rectus abdominis, 

 and other muscles, it has by others been regarded as a vestige of 

 the panniculus. One interesting variation to which it is liable 

 is that of forming a connection between the external oblique of the 

 abdominal region and the sterno-mastoid. Parsons has recently 

 shown that in Eodents the abdominal panniculus, on reaching 

 the axillary border of the pectoralis, divides into a superficial and 

 a deep stratum ; and from a very careful analysis of the detailed 

 relationships of the panniculus in these animals, he has adduced 

 strong reason for regarding the fascial sheath of the human 

 external oblique as its modified deep abdominal portion. He 

 further gives reasons for believing that the deep part of the 

 cervical panniculus has become incorporated in the sterno-mastoid, 

 and ultimately regards the sternalis as a vestige of that portion 

 of the panniculus which originally connected its deep cervical 

 and deep abdominal sections.] l 



Between the internal condyle of the humerus and the 

 olecranon, in Man, a fibrous band always runs, transversely, 

 below the superficial fascia which bounds posteriorly the deep 

 indentation in which the ulnar nerve lies. This band corre- 

 sponds with the epitrochleo-anconreus muscle, which is constant 

 in many Mammals ; it is only occasionally muscular in Man and 

 the Anthropoids, and then varies greatly in form and size. It 



1 [Parsons has farther simplified matters by suggesting that the pectoralis major 

 may be itself a derivation of the panniculus. Cf. Jour. Anat. and Phys., vol. 

 xxvii. p. 505.] 



I 



