BLISHA MITCHELL SCIENTIFIC SOCIETY. 19 



vol. II, p. 343; lamina oitalis of the ectopect oralis, W. 

 & G., pp. 239-240; ^6^r/o;Y^/^, /^/r/ 2 (partially), M., 

 p. 145; pectoralis, pari b (partially), G. & T., p. 30. 



Wilder and Ga^e divide the muscle into two subdi- 

 visions, cephalic and caudal. This division seems to 

 us an arbitrary one. We do not iind the muscle natu- 

 rally so divided. Mivart's part 2 apparently includes 

 our third pectoral and the posterior part of our second 

 pectoral. 



The fourth pectoral is a w^ide, thick mass, being 

 much the largest muscle of the group. ±\X its origin 

 it is a single, undivided muscle, though distally it splits 

 into two subdivisions, anterior and posterior, having 

 different insertions. 



The muscle arises from nearly the whole sternum. 

 The origin beg-ins just posterior to the presternum, 

 and includes all the mesosternebrae and the anterior 

 two-thirds of the xiphi-sternum. 



Of the two subdivisions into which the muscle splits 

 distally, the anterior is inserted on the great tuberosity 

 of the humerus, coming here into close connection with 

 the supra-spinatits. The insertion of the posterior sub- 

 division is complex. The chief part is inserted on the 

 proximal half of the ventral surface of the shaft of the 

 humerus, anteriorly by muscle fibres, posteriorly by 

 aponeurosis. The fibres forming the posterior portion 

 of this subdivision are inserted, along with the latis- 

 sinius dorsi, into the bicipital arch. Into the posterior 

 border of this subdivision run fibres belonging to the 

 great cutaneous muscle, th.Q paii7iiciihcs carnosus. 



Synonomy. Sterno-trochiterien plus premier chef 

 du grand pectoral, S.-D., p. 337, p. 341; ento-pecto- 

 rali^, W. & G., p. 2\\, pectoralis, part j, M. p. 147; 

 pectoralis, part c, G. & T., p. 30. 



