THE ABDOMINAL WALL. 



it is in this manner that ascites is produced. In addition to ascites, there are three other symp- 

 toms or signs of obstruction, dependent upon three other sets of veins aiding in the formation of 

 the portal circulation, which are readily understood if we are acquainted with the normal anas- 

 tomoses of these veins. 



1. There is a stasis in the venous hemorrhoidal plexus, in the neighborhood of the rectum, 

 from which the blood passes through the superior hemorrhoidal vein to the inferior mesenteric 

 and thus reaches the portal vein. In this manner hemorrhoids are produced. From this same 

 plexus the blood flows through the middle and inferior hemorrhoidal veins into the internal 

 pudic vein and finally reaches the inferior vena cava. 



2. There is passive congestion of the lesser curvature of the stomach and of the lower end 

 of the esophagus due to stasis in the coronary vein of the stomach. This may lead to dilatation 

 of the veins (esophageal varices) and even to rupture of these vessels with a consequent hema- 

 temesis; it is possible, however, for the blood in the esophageal veins to flow into the vena azygos 

 major. 



3. As a result of passive congestion and dilatation of the parumbilkal veins, the veins of the 

 abdominal wall also become dilated; these veins are partly arranged in a radiating manner about 

 the umbilicus, and the so-called caput Medusae is thus produced. [The Talma-Morrison opera- 

 tion for the relief of cirrhosis, whereby the great omentum is caused to form adhesions and venous 

 connections with the abdominal wall, is based on this venous anastomosis. ED.] 



The nerves of the abdominal wall are the terminal portions of the six lower intercostal 

 nerves, which pass beyond the costal margin and reach the rectus abdominis between the flat 

 abdominal muscles. In addition to these there are the ilio-hypo gastric and the ilio-inguinal nerves 

 from the lumbar plexus. All these nerves supply the muscles of the abdominal wall and give off 

 lateral and anterior cutaneous branches. There are also a number of nerves from the lumbar 

 plexus which are situated between the muscles of the posterior abdominal wall (iliopsoas, quad- 

 ratus lumborum, transversalis) and the peritoneum. They are the external cutaneous, the genito- 

 crural, and the anterior crural nerves. The external cutaneous nerve runs transversely across the 

 iliacus muscle toward the anterior superior spine of the ilium. The genitocrural nerve sub- 

 divides into a crural branch, to the skin of the subinguinal region, and a genital branch, passing 

 through the inguinal canal to the cremaster muscle. The anterior crural nerve is easily found in 

 the iliac fossa between the psoas and iliacus muscles and, with the exception of the sciatic, is the 

 longest nerve of the lower extremity (see page 161). [Pleuritic pain, particularly when located 

 low and near the diaphragm, is often referred to the abdominal wall along the terminations of the 

 lower intercostal nerves, and is sometimes mistaken for abdominal disease. ED.] 



The topography of the inner surface of the anterior abdominal wall, under normal tension, 

 is of great importance for the proper understanding of inguinal and femoral hernia (Figs. 56 to 

 58). The peritoneum is reflected over a number of underlying cords and thus forms folds which 

 have received special names. In the middle line the plica umbilicalis media passes upward from 

 the bladder to the navel; it is produced by the ligamentum umbilicale medium, the urachus of 

 fetal life, which is situated beneath the peritoneum. To either side of the bladder, the obliterated 

 remains of the hypogastric arteries, the ligamenta umbilicalia lateralia of adult life, form the 

 plica umbilicales laterales. Still more externally are the less pronounced plica epigastric^, which 



