1897.] NEW YORK ACADEMY OP SCIENCES. 337 



B. M. Pectoralis minor, Entopectoral. 

 (PI. XXXVIII. and XXXIV.) 



Origin. — Ventral surfaces and cephalic borders of 2d, 3d, 4th, 

 5th and 6th costal cartilages, and lateral margin of mesosternum 

 in the corresponding intercostal spaces. 



The origin from the 2d to the 5th costal cartilage is placed 

 close to the sterno-chondral junction, lying between the Ecto- 

 pectoral and the Supracostal muscle. Between the 5th and 6th 

 cartilages the line of attachment descends obliquel}^ across the 

 ventral portion of the 5th intercostal space, the muscle being 

 attached to the External Intercostal fascia and to the lateral 

 extremity of the 6th costal cartilage, close to the medial margin 

 of the Rectus abdominis. The origin throughout is almost di- 

 rectly muscular, only in the caudal portion by means of a deli- 

 cate tendinous lamella. The Entopectoral forms a muscle of 

 considerable size, the fibres converging somewhat to the humeral 

 insertion. 



Insertion of Pectoral Muscles. 

 CPl. XXIX.-XXXI. incl., PI. XXXII., fig. 1.) 



Clavicular j)ortion of Ectopecloral is closelj'^ united with the 

 Deltoid, the two muscles fusing along their adjacent margins. 

 The insertion is by a tendon, which fuses with the superficial 

 surface of the main pectoral tendon (see below). (PI. XXX., 

 fig. 1 ; PL XXXI., fig. 1 ; PI. XXXII., fig. 1.) 



The entire Pectoral insertion occupies the strongh' developed 

 lateral humeral crest, extending from the lateral tuberosity to 

 nearly the middle of the shaft of the bone, on a level with the 

 union of the bicipital heads. 



Connected with the Pectoral insertion is the Axillary Arch 

 (PI. XXIX.; PL XXX., fig. 1.) derived from the caudafborder 

 and ventral surface of the Latissimus dorsi. It forms a rounded 

 and slender muscular slip, lying upon the tendon of the Latissi- 

 mus dorsi, cephalad of the ventral origin of the Dorso-Epitroch- 

 learis, and terminates in a slender tendon, which fuses with the 

 deep surface of the Ectopectoral tendon (PL XXIX.,), hav- 

 ing crossed the Coraco-Brachialis and short head of the Biceps, 

 Avithout being connected with the fascia investing these muscles. 



The abdominal portion of the Ectopectoral constitutes a sep- 

 arate division (PL XXX.; PL XXXI., fig. 2; PL XXXII., 

 fig. 1.), turning laterad underneath the sternal portion, the fibres 

 of the two divisions crossing each other at an acute angle. It 



Transactions N. Y. Acad. Sci., Vol. XVI., Sig. 22, February 7, 1898. 



