CHEMICAL RELATIONS OF PROTEINE AND UREA. 525 



ance be made for nitrogen existing in a few other azotised 

 proximate principles in the urine, uric acid, kreatine, and 

 kreatinine, and for a small proportion of the same element exist- 

 ing in the alvine excrement, the amount of nitrogen in the urea 

 daily excreted with the urine would seem to be a good index 

 of the amount of flesh-formers required for the support of an 

 animal under the several different circumstances of existence. 



In all the nicer kinds of inquiry of this description, our facts 

 must, in the first instance, be drawn from what has been de- 

 termined in regard to man. Yet that is hardly an inconveni- 

 ence in a work that does not treat of one animal but of several 

 animals, respecting each of which it would have been tedious 

 to enter into the details of such a subject as now engages our 

 attention, and which, indeed, notwithstanding some existing 

 difficulties, promises to become an investigation of the utmost 

 practical value in reference to the rules for feeding the animals 

 of the farm. 



When the importance of familiarising our minds to views of 

 this kind is considered, it may not seem out of place to dwell 

 for a moment on such a speculative topic as the following : 



The chemical equivalent of proteine, which may be taken to 

 represent the muscular tissue, is 395, and the equivalent of 

 urea 60. Under the contraction of the muscular fibre that 

 is, during its disintegration oxygen is supplied by the blood, 

 as we may assume, without limit. If, then, we suppose 395 

 grains of proteine or muscular tissue to be disintegrated, there 

 will be afforded of 



Carbon, . . 216 grains. 



Hydrogen, . 27 



Nitrogen, . . 56 



Oxygen, . . 96 



395 

 But ] 20 grains, or two equivalents of urea, contain exactly the 



