USES OF SALT. 155 



equal amount is excreted in the urine ; when the food 

 contains less, a part of that which would otherwise be 

 excreted, is retained by the organism. 



All these statements are most unequivocally confirmed 

 by the composition of the urine in these different classes 

 of animals. 



64. 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 favor 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 am- 

 monia in their urine. This urine, moreover, has an 

 acid reaction. 



In contradistinction to this, we find, in the urine of 

 the herbivora, soda in predominating quantity ; and that 

 not combined with sulphuric or phosphoric acids, but 

 with carbonic, benzoic, or hippuric acids. 



65. These well-established facts demonstrate, that 

 the herbivora consume a far larger quantity of soda than 

 is required merely for the supply of the daily consump- 

 tion of blood. In their food are united all the condi- 

 tions for the production of a second compound of soda, 



