cxiv Journal of the Asiatic Society of Bengal. [N.S., XII, 



venous system), the liver sooner or later usually becomes diseased, 

 numerous cysts being developed. When only one renal afferent vein is liga- 

 tured, the kidneys remain approximately the same size. The reason why 

 the kidney which is relieved of venous blood does not increase in size is 

 probably the penetration of the venous blood of the other kidney across 

 the inter-renal vein into its relatively empty sinusoids and so it is but little 

 better off as regards oxygenated blood than the normal kidney. The 

 result of this experiment also is to cause a lot of additional blood to flow 

 into the anterior abdominal vein and so through the liver, and this last 

 organ usually becomes diseased. Since the two kidneys remain approxi- 

 mately equal in size in this experiment, it is evident that the presence or 

 absence of a venous supply, i.e., of a "renal-portal" system, is of no 

 importance — the arterial supply is all that matters. 



One problem it is at present difficult to solve is why the anterior 

 abdominal vein opens into the liver at all — why it does not retain its 

 primitive connection with one or both of the precaval veins. Too much 

 venous blood is, as we have just seen, bad for the liver and yet it would 

 appear from other experiments (and from the fact that it always is 

 connected with the liver) that the liver of frogs and toads at least needs 

 some blood from the hind legs poured into the hepatic-portal vein, 

 because in at least three toads in which the anterior abdominal vein had 

 been ligatured (and so all the venous blood from the legs and pelvis forced 

 through the " renal-portal " system) a new connection has become formed 

 in the course of two or three months and some of the venous blood from 

 th* - therefore poured into the liver as before. However, more work 



requires to be done upon the subject before these results can be regarded 

 as absolutely certain. 



From the a priori standpoint and from the collective evidence derived 

 from anatomical and physiological facts, we are justified in concluding 

 that the " renal-portal" system is functionless. The fact that numerous 

 hot-blooded active animals exist which are devoid of a " renal-portal " 

 system alone proves that this accessory is not necessary to the cold- 

 blooded inactive animals which possess it, and this conclusion is borne 

 out by the physiological enquiries above described. What then is the 

 meaning of the ' fc renal-portal " system? Except in those animals in 

 which the kidneys are small and therefore require but little room for their 

 development (Cyclostomes, primitive Elasmobranchs and some bony 

 fishes), the kidney in most animals is situated in a confined position, 

 being surrounded above and at the sides by dense connective tissue and 

 below by the peritoneum. Under these circumstances it is not surprising if 

 the numerous developing tubules tend to encroach upon the adjacent space 

 occupied by large thin-walled posterior cardinal sinuses, and as a matter 

 of common knowledge, the successive developments of the kidney (prone- 

 phros, mesonephros and metanephros) do follow the paths of these venous 

 sinuses, being, like the posterior cardinals, far apart anteriorly and close 

 together in the median line posteriorly ; in other words, the kidneys appear 

 to select the actual pat ft of the veins as a site for their development for th 

 simple reason that they have got more room in this region in which to 

 develop. It is this encroachment of the kidney-mass upon the lumen of 

 the posterior cardinal veins which produces the so-called ** renal-portal " 

 system, which as the evidence shows has nothing whatever to do with the 

 function of the kidney but is a mere quasi-accidental mechanical product of 

 the conditions of development. For this reason the author has renamed 

 the "renal-portal" system in his original paper as the "renal cardinal 

 mesh work' "—a term already adopted by Papin who has shown that one 

 important reason why the veins of the mammal have not been caught by 

 the kidneys, so to speak, is because the latter have shifted forwards and 

 so away from the veins, though the author believes that the extreme 

 concentration of the kidney substance and their divergence from the 

 middle line have been equally important factors.. 



We conclude then that the "renal-portal" system, or as I prefer to 



