Circulatory System 



:: 



blood the excess sugar, picked up by the blood in the walls of the di- 

 gestive tube, before it passes into the general circulation. This charac- 

 teristic hepatic-portal system is well developed in all vertebrates. 



Fig. 76. Venous system of a 

 urodele amphibian; ventral 

 view, (ab) Abdominal vein; (av) 

 venae advehentes; (erf) duct of 

 Cuvier; (ej) external jugular; 

 (h) heart; (tip) hepatic-portal; 

 (il) iliac; (j) jugular; (/) liver; 

 (/c) lateral cutaneous; (m) meso- 

 nephros; (p) postcava; {pc) 

 postcardinal ; (r) venae reve- 

 hentes; (sc) subclavian. (Cour- 

 tesy, Kingsley: "Comparative 

 Anatomy of Vertebrates," 

 Philadelphia, The Blakiston 

 Company.) 



Renal-Portal System. A second portal system, but less constant 

 in its degree of development, is related to the kidneys. In fishlike verte- 

 brates the caudal vein (derived from an embryonic subintestinal vein) 

 bifurcates at the base of the tail to form right and left branches (Fig. 

 71A-C). Each of these, except in fishes, joins with the iliac vein com- 

 ing in from the adjacent pelvic appendage. The resulting trunk passes 



