IN THE ORGANIC PROCESSES. 163 



amount of soda necessary to the formation of blood ; 

 and in most cases, among animals of this class, we 

 may assume that only as much soda as corresponds 

 to the proportion employed to form the blood is 

 expelled in the urine. 



When the carnivora obtain in their food as much 

 soda as suffices for the production of their blood, an 

 equal amount is excreted in the urine ; when the 

 food contains less, a part of that which would other- 

 wise be excreted is retained by the organism. 



All these statements are most unequivocally con- 

 firmed by the composition of the urine in these 

 different classes of animals. 



65. As the ultimate product of the changes of 

 all compounds of soda in the animal body, we find 

 in the urine the soda in the form of a salt, and the 

 nitrogen in that of ammonia or urea. 



The soda in the urine of the carnivora is found 

 in combination with sulphuric and phosphoric acids ; 

 and along with the sulphate and phosphate of soda 

 we never fail to find a certain quantity of a salt of 

 ammonia, either muriate or phosphate of ammonia. 

 There can be no more decisive evidence in favour 

 of the opinion, that the soda of their bile or of the 

 metamorphosed constituents of their blood is very 

 far from sufficing to neutralize the acids which are 

 separated, than the presence of ammonia in their 

 urine. This urine, moreover, has an acid re-action. 



In contradistinction to this, we find, in the urine 

 of the herbivora, soda in predominating quantity; 

 .M 2 



