1906. 



" REXAL-PORTAL SYSTEM. 



Text-fis-. 139. 



893 



— A&.C. 



R.RV 



R.S 



E.G.C, 



R.P.V. 



EXC 



Diao-ram sliowing- that the vascular supply of the kiduey elements is identical 

 "^ throughout the vertebrate series. 



I illustrates the portal theory o£ the amphibian kidney. II illustrates the actual 

 plan of cons ruction of the amphibian kidney. Ill illustrates the plan of con- 

 struction of the mammalian kidney.^A.G.C, afferent glomerular capillary; 

 A TC afferent tubular capillary ; C.U.T.,capillarisation i-ound urinary tubule; 

 E.G.C, efferent glomerular capillary; E.T.C. efferent tubular capillary; 

 G o-lomerulus; P.V.C, posterior vena cava; R.P.V., "renal-portal vem 

 (post-renal); R.S., renal sinusoids ; E.V., renal vem. 



a vein, a better chance of developing into the kidney than in 

 other places Why this should be the case may perhaps be 

 explained as follows : the walls of the veins, at the stage of growth 

 of the embryo when the kidneys become developed, are exceedingly 

 thin, consisting in the Frog, e. g., of merely a unilammar epi- 

 thelium and "it is on this account that the veins are easily 



