The-Lymphatic System in Human Embryos. 



83 



The posterior lymph sac shows on one side in Fig. 15, but much 

 better in Eig. 16. The posterior lymph sac is a double sac extending 



Fig. 15. Coronal section through the retroperitoneal sac of the human 

 embryo, at a level indicated on Fig. 21. X about 39. A., aorta ; K., kidney ; 

 S. 1. m., saccus lymphaticus mesenterica ; S. 1. p., saccus lymphatica posterior ; 

 V. c. i., vena cava inferior ; V. r., vena renalis. 



along the primitive sciatic veins. The reconstruction is made of the 

 left side, but shows where the left primitive sciatic vein joins the 



