DISEASES OF THE URINARY ORGANS. 



By JAMES LAW, F. R. C. V. S.. 

 Professor of Veterinary Science, etc., in Cornell University. 



Of the materials that have served their purpose in building up the 

 animal body or in sustaining the bodily temperature, and that are now 

 to be thrown out as waste, the greater part are expelled from the system 

 through the lungs and the kidneys. But the agents that pass out by 

 either of these two channels differ in the main from those passing by 

 the other. Thus from the lungs in the form of dioxide of carbon the 

 same gas that comes from burning of coal or oil there escapes most of 

 the waste material resulting from the destruction in the system of fats, 

 sugars, starch, and such other foods as are wanting in the element nitro- 

 gen, and do not form fibrous tissues, but go mainly to support animal 

 heat. From the kidneys, on the other hand, are thrown out the waste 

 products resulting from the destruction of the foods and tissues con- 

 taining nitrogen of, e. #., albumen, fibrin, gluten, casein, gelatin, 

 woody tissue, etc. While much of the waste material containing nitro- 

 gen leaves the body by the bowels, this is virtually such only of the 

 albuminoid food as has failed to b*e fully digested and absorbed, and 

 this has never formed a true constituent part of the body itself or of the 

 blood, but is so much waste food, like that which has come to the table 

 and been carried away again unused. Where the albuminoid food ele- 

 ment has entered the blood, whether or not it has been built up into a 

 constituent part of the structure of the body, its waste products, which 

 contain nitrogen, are in the main expelled through the kidneys, so that 

 these organs become the principal channels for the expulsion of all 

 nitrogen-containing waste. 



It would be an error, however, to infer that all nitrogenous food, 

 when once digested and absorbed into the blood, must necessarily 

 leave the system in the urine. On the contrary, in the young and 

 growing animal all increase of the fibrous structures of the body is 

 gained through the building up of those flesh-forming constituents into 

 their substance; in the pregnant animal the growth of the offspring 

 and its envelopes has a similar origin, and in the dairy cow the casein 

 or curd of the milk is a means of constant elimination of these nitrogen- 

 containing ageutt'. Thus, in the breeding and, above all, in the milk 



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