MAKTJAL OF CATTLE-FEEJDmO. 93 



oxygen, after it is taken into tlie Mood, remains for a time 

 in the system, suffices to sliow that the chemical phenomena 

 in the body diflter essentially from those outbide it, and 

 this is eonlirmed by the little we do know of the processes 

 themselves and by the intermediate pioducts, nmnbered by 

 hmidieds, which have been already disco\ered. 



Fortunately, however, for the purposes of cattle-feeding 

 we need only to know the final results of all these changes, 

 and these we have indicated above, and shall presently con 

 sider more in detail. 



§3. Excretion. 



As the result of the continued decompositions and alter- 

 ations going on in the body, we have a constant accumula- 

 tion of carbonic acid, water, and urea and other nitro- 

 genous products in the blood. 



The carbonic acid and urea are poisonous if allowed to 

 accumulate in the system, and the water would produce 

 injurious effects by diluting the blood, and means are 

 tlierefore provided for the removal of these substances 

 from the body. 



The Urine — In its course through the posterior part 

 of the body the blood passes through the kidneys, two 

 bean-shaped organs, in which the urea and other nitro- 

 genous substances coming from the decomposition of the 

 protein of the body are removed from it. The blood also 

 parts here with some of its water, and the excreted liquid, 

 the urine, passes from the kidneys to the bladder and is 

 thence expelled from the body at intervals. 



Besides urea, the urine of the herbivora contains, as has 

 been already noted, hvpjpv/riG (wid^ in which form a vary- 

 ing but small proportion of nitrogen is excreted by these 

 animals. In the carni\ora its place is taken by uric aady 



