PEACTICAL PHYSIOLOGY 



and has been found to remain constant in the same individual under 

 similar conditions, although it may vary in different individuals. It 

 is not affected by varying the amount of the diet provided always 

 that this be purin free. This can be seen from the following table : 



(Burian and Schur). 



This endogenous moiety comes from the nuclein of the tissues, but 

 just as in the case of the exogenous moiety, the whole of the liberated 

 purin does not reappear in the urine, a certain amount undergoing 

 rupture of its purin ring, and being excreted probably as urea. The 

 fraction, both of endogenous and exogenous purins, which is thus 

 further decomposed varies in different species of animals, man excreting 

 as urinary purins one half, carnivora only one twentieth ; and herbivora 

 (rabbit) one sixth. In different individuals of the same species, how- 

 ever, this factor remains constant, so that we can tell accurately how 

 much purin has been set free in the organism by multiplying the 

 endogenous moiety by 2 for man, or by 20 for carnivora, or by 6 for 

 herbivora. The chief organ in which this destruction, both of exogenous 

 and endogenous purins, ensues is the liver in dogs and the kidneys 

 in oxen. 



If the endogenous moiety be calculated out for each kilo body 

 weight, it will be found that it is greater in infants than in adults. 

 This is probably due to the fact that the tissue metabolism is more 

 active in the former, and consequently more nuclein is broken clown. 

 In certain blood diseases also (e.g. where the number of the poly- 

 morphous nucleated leucocytes is increased) an increase is noticed. 

 In this latter case, however, it is not the leucocytosis which causes 

 the purin increase, but rather, the leucocytosis and purin increase are 

 both due to some metabolic changes in the blood glands. 1 



Hippuric Acid. In herbivorous animals a large amount of nitrogen 

 is excreted as hippuric acid, but in man and the carnivora only traces. 



x ln a case of leucopenia (where the leucocysts were reduced to one fifth the 

 normal amount), Hutchison and I found the excretion of endogenous purins 

 of normal amount. 



