.. v ibin. 



side and the veins are emptied of blood by injecting them with salt 

 solution. 



The retroperitoneal - the largest of all the lymphatic sacs 



in the pig. As shown in Sevier's fig. 3 (43) it spreads oul lehind 



rectum and covers the entire area in the rooi of the mesentery 

 • II the two Wolffian bodies. It spreads over the ventral bui 

 of the Wolffia ■- as far as the edge of the reproductive glands. 



It was from injecting this sac thai Eeuer was able to study the devel- 

 opmenl of the lymphatics of the intestine. 



This Bac would give an excellenl opportunity to study the proa - 

 cavernization. Injections of it with silver citrate give beautiful 

 3, showing the endothelial-covered trabecular that cross its 

 lumen. Total preparations of the silvered sac remind one of the tri 

 uli' iii the wall of the cavity of the la-art. These trabecule, which 

 are tl the process of transferring the sacs into lymph 



glands, slmw especially well in sagittal sections of pig embryos 20-25 

 inn), long. 



2. Iliac Sao — Cisterns Chtli. 



I tan now bring Borne evidence to Bhow that the iliac lymphatics 



which drain the legs, tail ami abdominal wall, and the cistcrna chyli 

 which forms the lower part of the thoracic duct, arise togi ther as buds 

 from veins of the Wolffian bodies. A complete account of this process 

 nerd- ii more extensive illustration of the hlood vessels of the region 

 than I i .in give at this time. In the pig the lymphatics which hud 

 I/it' from the veins of the Wolffian body ami grow forward dorsal to the 

 aorta to form the cistcrna chyli ami caudalward along the edge of the 

 Wolffian body to form the iliac lymphatics, do nut begin until the 

 i mbryo is 22 mm. Inn-. | found that they arise from the niesone- 

 phritic veins because a direel puncture of the blood-filled buds entered 

 the main vein- and not the blood capillaries. In a litter of pigs which 

 measured '.'•'! mm. I washed out the blood vessels with Locke's solution, 

 am] then opened the specimens ami pushed one of the Wolffian bi 

 over toward the midline, a plexus of blood-filled lymphatics was 

 then readily seen dorsal to the aorta. I succeeded in puncturing some 

 of the hii i sels of the plexus forming the cisterna chyli in three 

 ■a the ink run from the lymphatics into the mesone- 

 phritic vein-. In all of these injections the cisterna chyli i- ohscured 

 travasations at the point f( injection, hut they all show the 



