414 PHYSIOLOGY CHAP. 



Our knowledge of the toxicity of urine has been considerably 

 advanced by .the work of Colasanti and his pupils (1895-96, 1899). 

 He experimented on dogs instead of rabbits, finding them more 

 resistant to the urinary poisons. Indeed, the mean urotoxic 

 coefficient for normal dogs is, according to Colasanti, O182, a 

 much lower figure than that determined by Bouchard for rabbits 

 ( = 0'465), showing that in dogs the resistance to these poisons is 

 2| times as great as that of rabbits. 



On comparing the protective function of the kidneys with that 

 of the liver, Colasanti saw that when the toxicity of the bile is 

 maximal, that of the urine is minimal, and -vice versa. The kidneys 

 and liver can, therefore, act vicariously as purgative organs, when 

 elimination of the endogenous poisons is inadequately performed 

 by the one or the other system. 



While studying the toxicity of the urine in diseases of the 

 liver in which the functions of this viscus are more or less altered, 

 Colasanti constantly observed urinary hypertoxicity, in ratio with 

 the degree of hepatic insufficiency. This increase of toxicity in 

 the urine is not in ratio with the amount of nitrogenous products 

 contained in it, which may increase or diminish according to the 

 different lesions of the hepatic parenchyma. It is therefore possible 

 from the increased toxicity of the urine to judge of the gravity of 

 the hepatic lesion, while its diminution may be a sign of recovery 

 of the hepatic functions. 



The experimental proof of the relations between the hepatic 

 and renal functions is seen in the fact that after gradual 

 occlusion of the portal vein the urine of the animals operated on 

 becomes hyper toxic like that of liver-patients, since in this case 

 the whole of the toxic substances otherwise eliminated by the bile 

 find no outlet other than the kidneys. The same fact also shows 

 that part of the biliary or urinary poisons are formed in the 

 intestine, whence they are absorbed and carried to the circulation 

 by the portal roots, and on reaching the liver are once more turned 

 out into the intestine with the bile. Colasauti, in fact, showed that 

 the bile secreted after occlusion of the portal system is so much 

 less toxic in proportion as the toxicity of the urine becomes greater, 

 although the chemical composition of the secretion may differ 

 little from the normal. 



The increase in the molecular composition of the blood observed 

 in uraemia, depends not so much on the mineral constituents 

 (bases, acids, salts) as on the organic compounds, which result 

 from tissue metabolism. As demonstrated by Viola and by 

 Bickel, the blood of nephrectomised or of uraemic patients does 

 not show any change in electrical conductivity. That the cause 

 of the uraemic phenomena lies in a specific toxic action of these 

 organic metabolites when retained in the body, and not, as Linde- 

 mann (1899) concluded, in the increased osmotic pressure of the 



