40 STUDIES IN COMPARATIVE ANATOMY. 



attached to the symphysis in its lower three-fourths, as well 

 as to the adjacent rami of the puhes. The two tendinous layers 

 form thus a kind of flattened pouch, communicating with the 

 abdominal cavity, and lined with the peritoneal membrane. The 

 free part of the tendon adheres to the inner or superior surface 

 of the thick abdominal aponeurosis. The muscle expands as it 

 passes forward, and again contracts towards its insertion into 

 the sternum. Eight tendinous intersections occur. 

 C. and L.— 287-8 (15). 



Obliquus externus takes origin from all the ribs, at least as far 

 forward as the third. The fibres pass downwards, and are inserted 

 into the abdominal aponeurosis. About six interdigitations with 

 serratus magnus may be made out. 



C. and L.— 274-5 (13); 276-7 (13); 282, upper figure (13). 

 Obliquus internus is less extensive than externus. The fibres 

 converge to a thin aponeurosis continuous with the sheath of 

 rectus, and closely attached to the outer surfaces of the cartilages 

 of the ribs. 



C. and L.— 276-7 (14); 287-8 (14). 



Transversalis abdominis arises by interdigitations with the 

 diaphragm, from the ribs between the second or third and the 

 seventeenth (inclusive) ; also from the eighteenth, nineteenth, 

 and twentieth ribs. The ventral portion takes origin as a thick 

 fleshy mass from the anterior superior spine of the ilium, and 

 from a small part of Poupart's ligament adjacent thereto. The 

 muscle passes thence horizontally inwards towards the middle 

 line, and is lost upon the inner surface of the abdominal fascia. 

 C. and L.— 287-8 (17). 



The Diaphragm arises by fleshy fibres from all the ribs from 

 the second or third to the seventeenth. As far back as the 

 thirteenth rib, the muscle is chiefly attached to the costal 

 cartilages; behind the thirteenth to the ribs themselves. The 

 crura arise from the three hindmost dorsal vertebrse by tendinous 

 processes. The tendon of the left crus is somewhat shorter than 

 the other. A ligamentum arcuatum, entirely tendinous, and 

 united to the central tendon, arches over psoas. 

 Not in C. aud L. 



Quadratus lumhorum arises from the two hindmost ribs, aud 

 passes to the innermost part of the crest of the ilium. 



