410 DISSECTION OF THE ABDOMEX. 



the external abdominal ring, which gives passage to the cord in the male, 

 and the round ligament in the female. 



Action. Both muscles taking their fixed point at the pelvis will bend 

 the trunk forwards as in stooping; but supposing the spine fixed they will 

 draw down the ribs. If they act from the thorax: they will elevate the 

 pelvis. 



Should one muscle contract, it will incline the trunk or the pelvis to 

 the same side, according as the upper or the lower attachment may be 

 movable : and it will turn the thorax to the opposite side. 



Parts of the aponeurosis. Besides the general arrangement of the 

 aponeurosis over the front of the abdomen, the student is to examine more 

 minutely the linea alba in the middle line ; the external abdominal ring 

 with the fascia prolonged from its margin ; and the rounded border named 

 Poupart's ligament. 



Linea alba (fig. 139). This white band on the front of the abdomen 

 marks the place of meeting of the aponeuroses of opposite sides. It ex- 

 tends from the xiphoid cartilage to the pubes, and serves as a ligament 

 between the chest and pelvis. Its breadth is wider above than below ; 

 and it is perforated here and there by small apertures, which allow pellets 

 of fat to protrude in some bodies. A little below the centre is the um- 

 bilicus, which projects now beyond the surface, though before the skin was 

 removed, a hollow indicated its position. 



External abdominal ring (fig. 135, c ). This opening is situate near 

 the pubes between the diverging fibres of the aponeurosis. It is somewhat 

 triangular in form, with the base of the crest of the pubes, and the apex 

 pointing upwards and outwards. The long measurement of the aperture 

 is about an inch, and the transverse about half an inch. 



Its margins are named pillars, and differ in form and strength. The 

 inner one, thin and straight, is attached below to the front of the symphy- 

 sis pubis, where it crosses the corresponding piece of the opposite side 

 that of the right muscle being superficial. The outer margin is the strong- 

 est, and is not straight like the inner, but forms a kind of groove for the 

 support of the spermatic cord : this margin is continuous with Poupart's 

 ligament, and is attached below to the pubic spine or tuberosity. A thin 

 membrane (intercolumnar) covers the opening, and is derived from some 

 fibres on the surface of the aponeurosis. 



The ring gives passage in the male to the spermatic cord, and in the 

 female to the round ligament ; and in each sex the transmitted part lies 

 on the outer pillar as it passes through, and obtains a covering from the 

 intercolumnar fibres. Through this aperture the inguinal hernia protrudes 

 from the wall of the abdomen. 



The intercolumnar fibres form a layer over the aponeurosis, and bind 

 together its parallel fibres, so as to construct a firm membrane. Inferiorly, 

 where they are strongest, a bundle is connected with the outer third of 

 Poupart's ligament, and is continued back to the crista ilii. At the ex- 

 ternal abdominal ring the fibres stretch from side to side, and becoming 

 stronger and aggregated together, close the upper part of that opening ; 

 and as they are prolonged on the cord from the margin of the ring, they 

 give rise to the membrane named intercolumnar fascia. On the left side, 

 where the fascia is entire, this thin covering will be manifest on the surface 

 of the cord, or on the round ligament in the female. 



Dissection. To see the attachments and connections of Poupart's liga- 

 ment, it will be necessary to reflect, on both sides of the body, the lower 



