142 THE CAT. [CHAP. v. 



which extends from the puhic symphysis to the anterior part of the 

 ventral margin of the ilium. 



In front of the pelvis the muscle ends in aponeurosis, which meets 

 that of its fellow of the opposite side in the mid -ventral common 

 fascia, which extends forwards to about the fourth rib. It passes 

 superficially to the rectus muscle, but its fascia is closely adherent to 

 the surface of the rectus. 



The deeper abdominal muscle, the internal oblique, is another sheet 

 partly muscular, partly membranous, but its fibres are directed 

 downwards, forwards and inwards. It arises from the lumbar fascia 

 on the outer side of the erector spinaa from the entire ventral margin 

 of the ilium and from the pubis. At its origin it leaves three aper- 

 tures at the brim of the pelvis. Through the uppermost of these the 

 psoas muscle passes out to the thigh. The next below is traversed by 

 the great vessels, and through the lowest the spermatic cord makes its 

 exit in the male. It is inserted inside the cartilages of the ribs, and, 

 behind the thorax, joins with its fellow of the opposite side its fascia 

 passing on the ventral side of the rectus to about the middle of the 

 abdomen, in front of which point it passes above the rectus. 



The deepest of the abdominal muscles, the transversalis, arises 

 from the cartilages of the ribs behind the diaphragm, from the 

 ventral margin of the ilium and from the fascia which invests the 

 under side of the erector spina^. It is therefore separated at its 

 origin by a wide interval from the origin of the internal oblique ; 

 the interval being occupied by the erector spina3 and by fat. The 

 muscular fibres of the transversalis extend vertically downwards 

 (i.e., transversely to the long axis of the body,) to the margin of the 

 rectus, within which its fascia extends i.e., on the dorsal surface of 

 the rectus. The abdominal nerves extend round the body between 

 this muscle and the internal oblique. 



liecttts abdominis. This is a long muscle which, arising from the 

 symphysis pubis, runs forwards in contact with its fellow of the 

 opposite side, to be inserted into the third rib, and thence on, by 

 aponeurosis, to the second and first ribs. It is enclosed ventrally 

 by the aponeuroses of the external and internal oblique from its 

 origin to the middle of the abdomen. Thence forwards it is enclosed 

 below by the aponeurosis of the external oblique, while above, it 

 is invested by the aponeuroses of the internal oblique and trans- 

 versalis (Fig. 79, E). 



The rectus is separated from its fellow of the opposite side by 

 a narrow interval, which is occupied by a tendinous cord the linen 

 alba. 



The fibres of the rectus are interrupted at intervals by very faintly 

 marked transverse tendinous intersections. 



Stcrnalis. This small muscle (Si 1 } arises from the anterior end 

 of the rectus abdominis close to the sternum, at the third and fourth 

 costal cartilages. It passes forwards and outwards, and is inserted 

 into the first rib jusf ventrally to the insertion of the scalenus primus. 

 A small second sternalis (Sfi) extends from the outer border of 



