888 MR. W. AVOODLAND OX THE [Nov. 27, 



body. Fi'om these facts it is evident that if, according to the 

 views now held, the " renal-portal system '"' possesses an excretoiy 

 function, then the kidney through the substance of which the 

 post-renal vein " ramifies " ought to be considerably larger than 

 one not so characterised on account of the larger blood-supply ; 

 especially will this difference in size be conspicuous when two such 

 differently-constituted kidneys exist in the same animal, since in 

 this case one kidney has the portal functions of two kidneys to 

 perform. But, again, the expectation is not justified by the facts, 

 as is for instance conspicuously shown by renal-portal vein ab- 

 normalities found in the Frog and described by Shore (7) and 

 myself (10). These abnormalities in short consisted of the entire 

 absence of a •' renal -portal system" on one side of the animal, i. e., 

 the kidney of one side was obviously supplied by the renal arteries 

 alone, and not, as usually appears to be the case, by the post-renal 

 vein as well, and yet, notwithstanding this, the two kidneys in 

 these abnormal frogs were in evei-y case equal in size : a fact 

 easily intelligible on the supposition that the arterial supply of 

 the kidney alone is concerned with excietion, but on no other 

 supposition. 



A third line of argument yields evidence equally as conclusive 

 as the two foregoing. The almost univei-sally adopted assumption 

 as to the portal nature of the renal cardinal meshwork is doubtless 

 based upon the belief that the post-renal veins form capillaries 

 in the substance of the kidneys in the same manner as the 

 hepatic-portal in the liver, this belief being supported by the 

 superficial aspect of the adult structure. But recent investigation 

 into the mode of development of the renal cardinal meshwoi-k 

 altogether disproves this svipposition. Shore (6, 9) has shown 

 that a radical difference of origin obtains "between the sinus-like 

 system of the mesonephros and that of the liver." Briefly stated, 

 " the former is the result of the penetration of the nephridia into 

 the cardinal vein, whilst in the liver there take place irruptions, 

 as it were, of capillary blood-vessels from the vitelline vein into 

 the solid mass of proliferated hypoblast." " The liver is originally 

 a solid mass of cells which has become fenestrated by blood-vessels, 

 and thus divided into a network of anastomosing cylinders," and 

 " the peculiarities of the liver in different types [of animals, active 

 ;i,nd inactive] depend upon the extent to which blood-vessels have 

 penetrated and subdivided it." That is to say, in the case of the 

 true portal system of the liver, in which the venous blood discharges 

 certain of its contents into the hepatic substance, the blood-vessels 

 actively find their way to all parts of the secreting mass ; on the 

 other hand, in the case of the pseudo-portal system of the mesone- 

 phros or " metanephros "' as the case may be, the blood- A^essels take 

 no such active part : on the contrary, the cavity of the venous sinus 

 itself becomes encroached upon by the growth of the kidney siibstance. 

 In the one instance in which we knoiv that certain substances are 

 extracted from the blood, the blood-vessels take an active part iu 

 penetration ; ii; tiie other, in which it is (illogically) assumed that 



