MUSCLES OF THE BODY. 153 
gus (g); this lies entirely in that part of the diaphragm which 
arises from the right crus (2). The fibres are again united 
ventrad of the cesophageal opening. 
(2) The sternocostal part (c, c’) takes origin from the 
xiphoid process and the last five ribs, by fleshy bundles which 
interdigitate with those of the transversus abdominis (2). The 
fibres converge to the central tendon (¢)., Between the crus 
of each side and the most dorsal of the costal fibres is the 
membranous interval (7) mentioned above. 
4. Abdominal Muscles. M. obliquus abdominis externus 
(Fig. 68, 2).—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. 
(2) From the lumbodorsal aponeurosis common to it and the 
internal oblique. The cranial fibres pass nearly ventrad, the 
caudal fibres caudad, arid 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 
laterodorsad. 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, #). Inner surface with the obliquus internus (Fig. 
