THE INGUINAL PLEXUS 355 



duct or the lower part of the vaginal canal. The other overlies the epigastric artery and 

 vein where they pass together from the iliacs on to the parietes of the abdominal cavity. 

 The glands are surrounded by dense concentrations of vascular substance (especially 

 the one lying against the prostate or vagina), which peripherally spread out in a diffuse 

 manner among the surrounding blood vessels and muscles. 



A similar diffuse network extends up the middle line of the body in close relation to 

 the lymph tract occupying that area. Although the disposition of the lymph tracts all 

 over the body was not studied and does not form the subject of the present paper, it 

 may be mentioned that vascular plexuses, similar to this one in the inguinal region, are 

 found wherever there is a concentration of lymphatics. These plexuses are diffuse and 

 ill-defined, and evidently different in nature, and thus probably in function, from the 

 two great retia in the thorax and basis cranii. The plexus in the inguinal region, however, 

 is so large and dense, and occupies such an extensive area, that some description of its 

 relations is justified. 



The rectus abdominis muscle has a threefold posterior attachment. An inner 

 portion, described by Carte and Macalister (pp. 223-4), narrows to a tendinous attach- 

 ment to the anterior chevron bones. A central slip is attached to the ilium of the 

 rudimentary pelvis. A third and outermost slip has a triangular insertion upon the 

 lumbar fascia between the ischio-caudalis and hypaxial muscles, immediately lateral to 

 the bulbus penis or to the vulva. There are thus two muscular arcades on each side of 

 the genital region admitting nerves and blood vessels. The outer arcade is formed by 

 the insertion of the rectus abdominis into the lumbar fascia on one side and the ilium 

 on the other. This arcade admits a stout vein from the superficial fascia of the pedicle. 

 This has plexiform anastomoses with the iliac veins. A stout lumbar nerve accompanies 

 this vein, but there is no complementary artery. The inner arcade is formed by the iliac 

 insertion of the rectus abdominis and the part passing to the chevron bones. It admits 

 the pudic arteries and veins with their accompanying nerves. These vessels, together 

 with the lumbar veins just mentioned and the epigastric arteries and veins, contribute 

 to the formation of the plexus around the two lymph glands. The plexus is continued 

 rostrally towards the two kidneys on either side of the middle line of the body beneath 

 the peritoneum, where it is in close association with the lymph glands which occupy that 

 tract. It receives small arteries from the aorta in this region and is drained by small 

 veins to the two large iliac branches of the postcava. In the region of the inguinal 

 plexus there are numerous sympathetic nerves, connected with the hypogastric nerve 

 plexus, and the stout somatic nerves to the genital region run through the inner arcade 

 of the rectus muscle on to the penis and clitoris. It did not appear, however, that the 

 vascular plexus was innervated by any of these, although they run through the midst 

 of it. The plexus can be dissected away from around them along their whole course, and 

 no small nervous twigs were found running to the plexus, such as were seen in the 

 thoracic and basicranial retia. 



