the Urine in Man and Carnivorous Animals. 469 



formation into living tissues they were not admitted into their 

 composition, they were not required in the constitution of the 

 latter. 



Now, among the products of the vital processes, which, to- 

 gether with the soluble phosphates, are removed from the or- 

 ganism through the urinary organs and channels, there are 

 two organic acids, namely, U7'ic acid and hippuric acid, both 

 possessing the property of combining with the soda or potash 

 of the alkaline phosphates, and acquiring in the combination 

 a higher degree of solubility than they possess, per se, at the 

 common temperature of the body. It is obvious that by the 

 accession of these two acids, and by their action upon the 

 phosphates of soda, an urate and a hippurate of soda must be 

 formed on the one hand, and an acid phosphate of soda on 

 the other ; and that, consequently, the urine must acquire an 

 acid reaction. 



But the presence of these two acids in the urine is not the 

 only cause of its acid nature ; there exists another cause which 

 tends powerfully to maintain and increase it. 



According to the preceding remarks we ought to find in 

 the urine all the soluble salts of the food, as well as a small 

 amount of the phosphate of lime, which is soluble to a certain 

 extent in acid fluids, together with magnesia. The amount 

 of these latter substances will be in proportion to their solu- 

 bility in acid phosphate of soda. The other insoluble salts 

 of the aliments we ought to find in the faeces. In other words, 

 assuming that the materials composing the aliments become 

 converted into oxygen compounds, that is, are burnt in the 

 organism, we ought to find in the urine all the soluble salts 

 of their ashes, and in the faeces all the insoluble salts. Now, 

 upon comparing the constitution of the ashes of the blood or 

 of the aliments, or, rather, the salts contained therein, with 

 those contained in the urine, we find that there exists a stri- 

 king difference between their respective amount of sulphates. 



According to the analyses of the ashes of the grains of 

 wheat and rye*, the urine of an individual feeding exclusively 

 upon bread ought not to contain a single trace of a sulphate, 

 whilst the urine of an animal fed upon peas or beans ought 

 to contain sulphates together with phosphates in the propor- 

 tion of 9 of the former to 60 of the latter. Finally, as flesh 

 contains no soluble alkaline sulphate (broth does not yield 

 any precipitate of sulphate of barytes when tested with salts 

 of barytes), the urine of carnivorous animals ought to be 

 equally free from soluble sulphates. We find, on the con- 



* Annalen der Chemie, vol. xlvi., p. 79. 



