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



teric branch (fig. 2, V. 1. mes.), is large and supplies the rest of the small intestine as 

 well as the coils of the large intestine, the ascending, transverse, and descending 

 colon. 



Posterior portion of sac. Arbitrarily, the retroperitoneal sac was divided at the 

 hilum of the kidney into an anterior and a posterior portion, but even at the anterior 

 pole the sac is seen to broaden so that it occupies the interval between the mesial 

 borders of the two organs. In earlier stages it extends to the hilum of the Wolffian 

 body. In later stages (7 to 8 cm.) vessels from the lateral side of the sac enter the 

 kidney at the hilum in company with other lymphatics from the dorso-lateral side 

 of the aorta (fig. 1, V. 1. ren.) . In earlier stages, when the Wolffian bodies are large 

 and completely hide the kidneys in a ventral view, the whole posterior lateral edge 

 of the sac sends a sheet of parallel blunt processes, transverse to the axis of the 

 embryo, which extend a short distance on both the dorsal and ventral capsules of 

 the Wolffian bodies, as well as entering the mesial border in company with the 

 blood-vessels of the glomeruli. At the stage shown in figure 1 the sac does not 

 extend to the mesial border of the Wolffian body, but only a short distance over the 

 ventral surface of the kidney, where numerous stout vessels accompanj' the meso- 

 nephric veins. As these veins atrophy the satellitic lymph-vessels disappear. The 

 remnants of the blunt processes are here shown passing obliquely backward to the 

 posterior part of the Wolffian body and leading to a characteristic plexus along the 

 medial ridge of the Wolffian body the gonadal plexus (fig. 1, V. 1. gon.). Thus, of 

 the numerous blunt processes going to the Wolffian body, only those related to the 

 gonads and other reproductive structures persist; the others disappear and this 

 gonadal plexus becomes the genital branch, appearing in the stage shown in figure 1 

 as a fine plexus arising from the retroperitoneal sac at its lateral border, just cephalad 

 to the bifurcation of the aorta, and passing laterally to the posterior medial end of 

 the Wolffian body. Here part of the vessels turn sharply and course cephalad along 

 the mesial border of that organ forming a fine plexus about the gonadal blood- 

 vessels. This anterior branch continues to the hilum of the gonad which it supplies. 

 The genital branch also forms a network over the caudal end of the Wolffian body, 

 as well as giving off branches to the Mtillerian and Wolffian ducts and the gonadal 

 ligament. In the earlier forms the sac sends lymphatics to the medial side of the 

 umbilical cord, where they anastomose with those from the posterior portions of the 

 iliac sacs. In the later stages they fail to inject. 



Thus the peripheral spread of the lymphatic vessels from the posterior part of 

 the retroperitoneal sac has been described; it remains only to mention the third 

 efferent connection, which arises from the posterior end of the retroperitoneal sac, 

 passes laterally to the outer side of the umbilicus, and then turns dorsally to join 

 the caudal ends of the iliac sacs. 



