240 ANATOMICAL TBOBNOLOQY. '' ' 



the muscle, but laterad of it the plane becomes oblique, with a 

 dorso-cephalic direction which is more marked nearer the humerus. 

 Transect by an ecto-ental incision opposite the artery. 



In reflecting the sternal part, note the close union of the ental 

 surface near the meson with the ectal surface of the sterno-mastoi- 

 deus. In reflecting the humeral part, note that, excepting at the 

 caudal border, the muscular flbers cease along the ventral margin 

 of the trochiter. 



§ 653. Origin. — The caudal two thirds is from the lateral sur- 

 face of the prsesternum cephalad of the attachment of the first costi- 

 cartilage ; the cephalic third from the median raphe and from the 

 ectal surface of the sterno-mastoideus . 



Insertion. — Along a curved line upon the cephalic surface of the 

 proximal fourth or fifth of the humerus (Fig. 68, 69). The line of 

 insertion begins 3-4 mm. proximad of the proximal end of the inser- 

 tion of the ectal lamina, and sometimes very slightly ventrad of it. 

 The distal two thirds of the line extend dorso-proximad to a point 

 just ventrad of the slight elevation {Tbcl. micostale, see M. mico- 

 stalis), distad of the Fs. trochiteriana (Fig. 45, B), where it usually 

 turns slightly ventrad so that the proximal third forms an angle of 

 20-30 degrees with the rest. The line ceases about 3 mm. from the 

 proximal border of the trochiter at the edge of the insertion of the 

 M. supraspinatus. 



LAMINA SNTALIS, DV. CAUDALIS. 



§ 653. Synonymy. — "ie second chef Hu large pectoral, sa partie posUrieure," S.-D., 

 A, II, 343 ; pectoralis, part S (in part), Miv., B, 146. 



Figures. — Part of ectal aspect (71, right side) ; humeral end, reflected (73, left side) ; 

 insertion line (69). 



General Description.— The widest and longest portion of the 

 ectopectoralis, excluding of course the pecto-antebracMalis ; from 

 the cephalic part of the sternum to the second and third fifths of 

 the ventral border of the humerus. 



Dissection.— The cephalic border has been indicated during the 

 dissection of the cephalic division, and the caudal border during the 

 dissection of the caudal division of the pecto-antebracliialis. Lift 

 both borders, but dissect up the middle of the muscle from the 

 cephalic toward the caudal border, using the tracer and the handle 

 of the scalpel so as to avoid cutting the subjacent muscles ; then 

 transect, and reflect both ends until bone is reached. 



