270 BIOLOGY. [Book ii. 



It is denser, more charged, more coloured during digestion, more 

 colourless, on the contrary, and holding in solution fewer pro- 

 ducts of excretion during the first infancy, when assiimlation 

 predominates over disassimilation, and when the needs of growth 

 fix in the economy, in great quantity, the nutriments which 

 penetrate thereinto. 



After violent exercise, the urea, the phosphates, and the sul- 

 phates notably augment in the urine; for there is a greater 

 consumption of albuminoidal substances. 



Abstinence brings the same results; for then the animal is 

 noui'ished at the expense of his own tissues ; but in this last 

 ease the augmentation of the phosphates and sulphates is simply 

 relative. 



Excellent observations and analyses, especially those of Dr. 

 Byasson, have put it beyond doubt, that all intellectual activity, 

 how little soever energetic, has as corollary a corresponding 

 augmentation of the urinary phosphates. Every organic act has, 

 in truth, for basis an oxydation of the tissue, of the anatomical 

 element which operates. The brain is subject to this law, like 

 every other organ ; but, as we shall see by and by, it is very 

 rich in phosphates. It is therefore perfectly natural that its 

 disassimUation should give birth to phosphorised products of 

 excretion. 



As we have already mentioned in a preceding chapter, the 

 urine of the herbivora is generally alkaline, and richer in hip- 

 puric acid and" in hippurates. That of the carnivora is habitually 

 acid, and the urates and the uric acid are in larger proportion 

 therein. But, as we have indicated, there is nothing fixed and 

 immutable. Every herbivore, subjected to an animal alimenta- 

 tion, has the urine of a carnivore, and simple abstinence itself 

 suffices to produce this result. 



An abundant animal alimentation has for result greater pro- 

 duction and excretion of uric acid and urates. On the contrary, 

 in abstinence the uric acid disappears and the urea is excreted 

 in greater quantity. The wvea,, product of an oxydation more 



