MUSCULAR SYSTEM 113 
this point the muscle runs perpendicularly along the triceps 
(radiating out into the surrounding fascize) 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 
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 pectorals 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 Rodents 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. ]? 
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-anconzus 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 further simplified matters by suggesting that the pectoralis major 
may be itself a derivation of the panniculus. Cf. Jour. Anat. and Phys., vol. 
XXvil. p. 505. ] 
I 
