226 ANATOMICAL TECHNOLOGY. 



humeralls, and avoid cutting the ental, thicker and darker colored 

 laiissimus (Fig. QQ\ the cex)halic part of which, was exposed in the 

 dissection of the spino-lrapezlus. 



Begin to lift the flap at the dorsimeson ; remove the fat and con- 

 nective tissue from the ental surface of the derino-humeraUs, and 

 note that its libers have nearly the same direction as those of the 

 latlssimus. When the caudo- ventral border of the latissimus is 

 reached, a little ventrad of the middle of the incision, be careful not 

 to lift with the skin and dermo-liumeralis, the thin dorso-caudal 

 margin of the M. xipM-Jiiimeralis (Fig. 72), a member of the pecto- 

 ralis group of muscles, which arises at the meson, and sometimes 

 adheres quite closely to the dermo-hitmeralis. 



General Description. — As stated by Straus-Durckheim (A, I, 

 251), "this muscle covers as a mantle the whole thorax and abdo- 

 men, . . . but differs from the skin-muscles proper in the attach- 

 ment of one end to the skeleton;" this attachment, however, is 

 only indirect. 



Dissection. — The cephalic and shorter border of the muscle may 

 be seen on the ental surface of the skin along a dorso-ventral line 

 from the 2d or 3d thoracic spine to the axilla. The caudo-ventral 

 border is less distinct, but may be detected 1-2 cm. from the meson. 

 Connect the two borders by an incision 3-4 cm. from the brachium. 

 Leave the caudal portion of the muscle upon the skin, but carefully 

 dissect up the narrower and thicker brachial part, freeing both its 

 ectal and ental surfaces from fat and connective tissue. Note that 

 it not only overlies the corresponding part of the latissimus, but 

 that its ental surface becomes intimately united with the ectal sur- 

 face of that muscle. 



§ 630. Origin. — From the skin, along an oblique line extending 

 ventro-cephalad from about the middle of the length of the jDelvis 

 upon the caudal aspect of the meros as far as the knee ; also along 

 a line which is just laterad of the dorsimeson opposite the 2d or 3d 

 thoracic spine, but which gradually leaves the meson as it extends 

 caudad to join the pelvic line already mentioned. 



Insertion, — From the broad origin above described the fasciculi 

 converge ventro-cephaJad toward the caudal aspect of the brachium. 

 The muscle becomes narrower and thicker, and less closely attached 

 to the skin. Near the dorsal border of the bracliium it joins the 

 ectal surface of the subjacent latissimus. The dorsal border, 1-1.3 

 cm. wide, is attached directly by muscular fibers, but the remain- 



