Comparative Morphology of Chordates 



OBLIQ. ABOOM. EXT,' 



PECT ABDOM>'' 



OBLIQ ABOOM EXT. 



Fig. 455. Pectoral and abdominal musculature of the rhesus monkey. (Cour- 

 tesy, Hartman and Straus: "Anatomy of the Rhesus Monkey," Baltimore, 

 Williams & Wilkins Co.) 



of thin layers whose muscle-fibers extend parallel to the surface of the 

 layer. Certain of these layers extend in unbroken continuity through- 

 out the greater part of the abdominal wall of one side of the body, but 

 the layers of right and left side are separated in the midventral region 

 by a median band of connective tissue, the linea alba. Most constant 

 of these abdominal layers are the external oblique, whose fibers 

 extend diagonally ventrocaudad (Figs. 454, bottom; 455) ; the internal 

 oblique, whose fibers extend diagonally ventrocephalad ; and, still 

 deeper, the transverse, whose fibers run in approximately transverse 

 direction (Fig. 458). Lying close upon either side of the linea alba is a 

 pair of rectus muscles extending from the anterior region of the 



