FIGURE 20 



20 Transverse section of upper abdominal region of a 17 mm. cat embryo, show- 

 ing developing components of ascending lumbar lymphatic trunks and of mesen- 

 t eric sac in relation to embryonic veins in the roo t of the dorsal mesen Lery and their 

 relation to the cardinal collateral venous channels (series 258, slide XXIII, section 



34), X 75. 



1 Sympathetic nerve. 



7 Aorta. 



51 Mesenteric lymphatics. 



58 Ureters. 



61 Iliac vessels. 



62 End gut. 



63 Ventral division of cloaca (urinary bladder). 



64 Wolffian ducts. 



66 Umbilical arteries. 



67 Right postcardinal vein. 



68 Left postcardinal vein. 



74 Cardinal collateral veins. 



75 Ascending lumbar lymphatic trunks. 



