M. DERMO-HUMERALIS. 225 



Note, but do not remove, the carotid artery, and the nervous trunk 

 representing the conjoined NN. vagus and sympatliicus (Fig. 107). 



628. Origin. The larger and constant head arises by fleshy 

 fibers from the ventral surface of the atlantal transverse process 

 along an oblique line extending from the junction of the process 

 with the body of the vertebra, 3-4 mm. from the meson, latero-caudad 

 to a point about 3 mm. cephalad of the caudo-lateral angle of the 

 process. This line of origin is 6-8 mm. long, and is nearly parallel 

 with the oblique meso- caudal border of the arthral surface in con- 

 tact with the axis. 



The smaller and less constant head is about 3 mm. wide and is 

 the more direct continuation of the ventral border of the muscle. 

 Opposite the latero-cephalic angle of the transverse process it be- 

 comes a thin flat tendon which is closely applied to the ventro- 

 lateral aspect of a muscle, the M. rectus anlicus capitis, which 

 extends along the ventral side of the vertebrae, and is inserted with 

 it into the basioccipital bone nearer the bulla (Fig. 57) than the 

 meson, and about midway between the jugular foramen (Fig. 57, 

 Fm. j.) and the cephalic angle of the bulla. This, the occipital 

 head of the muscle, is sometimes absent, and other irregularities 

 have been observed in the cephalic end of the muscle. 



Insertion. By a strong tendon 1-2 mm. long and a little nar- 

 rower than the muscle, upon the ectal surface of the metacromion 

 (Fig. 45, 67), close to its free border. The dorsal border slightly 

 overlaps the ventral border of the acromio-trapezius near its inser- 

 tion, and the ventral border is firmly joined by a strong fascia with 

 the claw-trapezius. 



M. DERMO-HUMERALIS. 



629. Synonymy. " Dermo-humeral," S.-D., A, II, 251 ; part of the " pannicule 

 charnu," Ch., A, 200; part of the fleshy pannide, Ch. (Fl.), A, 186 ; part of the pannicu- 

 lus carnosus, Miv., B, 136 ; not represented in man. 



Figures. Humeral part, ectal aspect (66, 74) ; partly reflected (67, 72, 73). 



Posture. Latericumbent, the ventral region toward the dis- 

 sector ; a block transversely under the thorax, just caudad of the 

 elbows. 



Exposure. Connect the last (13th) thoracic spinous process 

 with the ventrimeson by a dorso-ventral incision. Be careful to 

 divide only the skin, with the subcutaneous fat and connective tis- 

 sue, together with a thin sheet of pale muscular fibers, the dermo- 

 15 



