MUSCLES OF THE BODY. 153 



gus {g) ; this lies entirely in that part of the diaphragm which 

 arises from the right crus {a). The fibres are again united 

 ventrad of the oesophageal opening. 



{b) The sternocostal part (r, c') takes origin from the 

 xiphoid process and the last five ribs, by fleshy bundles which 

 interdigitate with those of the transversus abdominis (/). The 

 fibres converge to the central tendon [e). Between the crus 

 of each side and the most dorsal of the costal fibres is the 

 membranous interval (d) mentioned above. 



4. Abdominal Muscles. M. obliquus abdominis externus 

 (Fig. 68, /). — A large, thin sheet of muscle covering the whole 

 abdomen and part of the thorax ventrally. 



Origin. — {a) From the last nine or ten ribs by means of as 

 many tendons, which are interconnected to form arches that 

 span the slips of the serratus anterior. The muscle-fibres 

 arise from these tendons and from their intervening arches. 

 (/'') From the lumbodorsal aponeurosis common to it and the 

 internal oblique. The cranial fibres^pass nearly ventrad, the 

 caudal fibres caudad, and the intervening fibres take an inter- 

 mediate course. The fibres end in a thin aponeurosis of inser- 

 tion along a curved line which passes at first caudad and then 

 latcrodorsad. The aponeurosis fibres continue in the direction 

 of the muscle-fibres to the 



Insertion into the median raphe ventrad of the sternum from 

 the insertion of the seventh costal cartilage to the xiphoid 

 process, into the linea alba from the sternum to the pubic 

 tubercle, and into the turbercle and the cranial border of the 

 pubis. Caudad of the xiphoid process the aponeurosis is closely 

 united to the superficial layer of the internal oblique, where it 

 forms the outer layer of the sheath of the rectus abdominis. 

 Laterad of the pubic tubercle the tendon is perforated by the 

 inguinal canal. In the cat neither the caudal part of the muscle 

 nor its tendon is attached to the ilium, as it is in man and the 

 dog, so that no Poupart's ligament, or inguinal ligament, is 

 formed. 



Relations. — Outer surface with the cutaneus maximus, 

 the integument, and near the origin with the latissimus dorsi 

 (Fig. 68, VI). Inner surface with the obliquus internus (Fig, 



