450 A MANUAL OF ANA TOMY. 



The iliohypogastric nerve (Fig. 89) appears through 

 the internal oblique muscle just above, and an inch internal 

 to the iliac spine, and takes a course downward and forward 

 upon the internal oblique. 



The linea semihmaris (Fig. 89) will be seen at the outer 

 border of the rectus muscle. It is formed by the junction 

 of the aponeuroses of the internal oblique and transversalis 

 muscles. The aponeurosis of the internal oblique divides into 

 two layers at the outer border of the rectus muscle for its 

 upper three-fourths. Half of the aponeurosis passes behind 

 the rectus with the whole of the transversalis for this dis- 

 tance, and half in front with the whole of the external ob- 

 lique for the same extent. In the lower fourth the blended 

 aponeuroses of all three muscles pass in front of the rectus. 



Its sheath behind in the lower fourth is then only com- 

 posed of the Fascia of the Transversalis, see page 454. 



The semilunar fold of Doug-las (Fig. 94) is the free 

 margin of the posterior sheath of the rectus muscle. It is 

 about midway between the umbilicus and the pubes (and 

 of course behind the rectus). 



The aponeurosis of the external oblique joins the inter- 

 nal oblique inside of the linea semilunaris. 



Actions of Internal Oblique. Same as for External, q. v. 



Nerve supply. See page 453. 



DISSECTION. 



Incise the internal oblique muscle transversely inward from the anterior 

 superior iliac spine to the linea semilunaris, and vertically from the same point 

 to the lower border of the ribs, then along their margin until the outer edge 

 of the rectus is reached. Reflect this quadrilateral flap of internal oblique, 

 being careful to leave the nerves and arteries resting upon the transversalis. 



Do not attempt to separate the lower triangular portions of the internal 

 oblique from the transversalis, as they are so intimately blended together that 

 the separation cannot be done properly. 



The posterior portion : of the internal oblique can be cut away from the 

 ribs and crest of the ilium and left hanging by the lumbar fascia. 



