1888.] NATURAL SCIEKLCES OF PHILADELPHIA, 143 



rnerus, and blending with the cephalo-humeral at a point 3 J inches 

 from the head of the humerus, are inserted in common with the lat- 

 ter on the outer lip of the bicipital groove for a distance of 4 inches. 

 Beginning at a point 8 inches from the manubrium and 3 inches 

 from the middle line of the sternum, its posterior border begins to be 

 involuted, and this fold becoming deeper as it goes outward is finally 

 inserted by an aponeurosis 2 inches wide, immediately beneath the 

 superficial layer. 



The posterior (" deep") division of the anterior thoracic nerve 

 appearing at the anterior edge of this fold, runs backward over its 

 superficial aspect to the line of folding and then turns forward on 

 the deep surface of the main snj^erficial mass, where it is finally lost. 



Upon close inspection the posterior border of this mass is seen to 

 be split ofi" as a separate band, which is several inches wide at its 

 origin, comprising most of the part rising from the abdominal mus- 

 cles, but rapidly narrows as it passes outward until it is only about 

 f inch wide. This ventro-humeral slip is carried under with the 

 fold just mentioned, forming at first its anterior edge ; out toward 

 the insertion, however, the widening fold extends itself between the 

 ventro-humeral and the superficial pectoralis major, so that for a 

 space its edge coincides with that of the former, and finally, the ven- 

 tro-humeral, instead of forming the anterior border of the involution, 

 comes to occupy the middle of its deep surface; the two blend and 

 insert in common. The fold is thus seen to be complete without 

 the ventro-humeral slip, though the latter appears to be an intrinsic 

 part of it. The ventro-humeral and the main superficial mass (p. 

 major) are quite distinct down to their origins, but the line between 

 them is so obscure as to have escaped my notice at first. 



The concavity of the involution shows a disposition to split off a 

 number of narrow fasciculi. The outer edge of the posterior end of 

 the ventro-humeral approaches closely to the latissimus dorsi, but 

 there appears to be no connection between them. As, however, the 

 skinning had been I'ather deep behind the axilla, there might have 

 been connecting slips in that region which did not show in the spec- 

 imen. 



The distal end of the pectoralis minor (see below) lies immediately 

 anterior to the involuted fold and in the same plane with it. The 

 muscle rises from the sternal ends of the costal cartilages, from the 

 second to the seventh inclusive, and pursuing an oblique course out- 

 ward and forward, inserts by a thin aponeurosis which partly at- 



