30 FATE OP PRIMARY LYMPH-SACS IN ABDOMINAL REGION OF PIG, ETC. 



the umbilical cord, where it anastomoses with a similar vessel from the retroperi- 

 toneal sac. It also sends lymphatics ventrally, in company with the vessel to the 

 umbilical cord, to break up into smaller vessels over the posterior pole of the Wolffian 

 body, where it evidently supplies part of the Mullerian and Wolffian ducts (shown on 

 the left side of fig. 1) just at the inferior pole of the Wolffian body. This seems an 

 important point, for, as will be noticed in figure 1, the lymphatics of the gonad 

 itself are related primarily to one set the ventral lymphatics, derived from those 

 of the Wolffian body while the lymphatics of the accessory genital organs are shown 

 to be embryonically related to two sets of lymphatics those from the ventral or 

 retroperitoneal sac, and those from the dorso-lateral or iliac sacs. 



The posterior trunk then continues as a definite group of lymphatics, the com- 

 mon iliac trunk following the artery of that name. It terminates by dividing into 

 two smaller branches, the more important of which is the femoral or external iliac. 

 These terminal vessels of the posterior trunk are satellites of the main arteries of the 

 pelvis and hind-limb (fig. 1). In the stages at which the injections were made, the 

 first or primitive arrangement of the blood-vessels of the posterior part of the body 

 has changed, so that the blood comes from the aorta by way of the two common 

 iliac vessels, which arise dorso-laterally just anterior to the origin of the umbilical 

 arteries. Each passes caudally, lateral to the umbilical cord, sending a branch (the 

 ilio-inguinal) around the pole of the kidney. At or just beyond the passage into 

 the pelvic wall it divides into two main vessels. One of these, the internal iliac or 

 hypogastric, which runs dorso-medially, divides into a number of terminal branches. 

 The other, the femoral or external iliac, continues ventrally to the front of the hind- 

 limb. At the proximal end of the femoral the now a trophic sciatic artery arises. 



The common iliac lymphatic trunk broadens considerably at the bifurcation of 

 the common iliac artery and then divides into a ventral and dorsal branch. The 

 dorsal trunk the internal iliac or hypogastric (fig. 1, T. hypo.) accompanies the 

 internal iliac artery and terminates by breaking into a number of vessels, satellites 

 of the lesser arterial branches. A short distance from its origin the ventral branch 

 the femoral or external iliac (T. il. ext.) sends a few lateral branches with the 

 sciatic artery. It divides shortly, many of the vessels turning medially to form the 

 inguinal trunk (fig. 1, V. 1. ing.) which drains a plexus of lymphatics along the 

 inguinal ligament. This plexus is converted into two large elongated nodes, one 

 situated more deeply than the other. These break up into a group of deep and super- 

 ficial nodes which drain the lower abdominal wall, external genitalia, perineum, 

 mesial side of the thigh, and practically the whole of the lower extremity. The 

 remainder of the vessels of the femoral trunk (fig. 1, V. 1. fern.) continue caudally, 

 following the femoral artery in its course in the leg. 



