2I 4 



ABDOMEN 



internal intercostal muscles -indeed, they will be observed to 

 be directly continuous with the fibres of the internal inter- 

 costal muscles of the lower two spaces. The lowest fibres, 

 those springing from the inguinal ligament, arch downwards 

 and medially, and join with the lowest fibres of the trans- 

 versus in a flat tendon, called the falx inguinalis (O.T. con- 

 joined tendon}, which is inserted into the pubic crest, and into 

 the ilio-pectineal line, for fully 12.5 mm. (half an inch) of its 

 extent, behind the lacunar ligament and the reflex inguinal 



ligament (Figs. 101 

 and 97). The middle 

 fibres pass upwards 

 and medially, and 

 end in a strong 

 aponeurosis, which ex- 

 tends from the inferior 

 margin of the thorax 

 to the pubis. By that 

 aponeurosis they gain 

 insertion into the in- 

 ferior borders of the 



cartilages of the 

 FIG. 97. Diagram to illustrate the relation , , . , , 



of the lower border of the Internal Oblique Seventh and eighth 

 Muscle to the Cord, the Falx Inguinalis, ribs and the xiphoid 

 and the Inguinal Canal. process, and into the 



linea alba throughout 

 its entire length. The 

 manner in which the 

 aponeurosis reaches 

 the middle line requires special description. 



At the lateral margin of the rectus muscle the aponeurosis 

 of the internal oblique splits into two layers a superficial 

 and a deep. The superficial layer of the aponeurosis passes in 

 front of the rectus, and has already been seen to fuse with 

 the aponeurosis of the external oblique muscle. The deep 

 layer is carried medially behind the rectus, and becomes 

 incorporated with the subjacent aponeurosis of the transversus 

 muscle. But this arrangement does not hold good lower 

 down than a point about midway between the umbilicus and 

 the pubis. Below that point the aponeurosis does not split, 

 but passes entirely in front of the rectus to join the apo- 

 neurosis of the external oblique. 



O.I. Internal oblique muscle. 

 C.T. Falx Inguinalis. 



The position of the subcutaneous inguinal ring 

 indicated by a dotted outline. 



