132 UKIC ACID AND UREA DERIVED 



especially nitrogenized food, may have a direct influence 

 on the formation of urinary calculi. There are no 

 reasons which support this opinion, while those opposed 

 to it are innumerable. It is possible that there may be 

 taken, in the food, a number of matters changed by the 

 culinary art, which, as being no longer adapted to the 

 formation of blood, are expelled in the urine, more or 

 less altered by the respiratory process. But roasting 

 and boiling alter in no way the composition of animal 

 food. (34) 



Boiled and roasted flesh is converted at once into 

 blood ; while the uric acid and urea are derived from 

 the metamorphosed tissues. The quantity of these 

 products increases with the rapidity of transformation 

 in a given time, but bears no proportion to the amount 

 of food taken in the same period. In a starving man, 

 who is any way compelled to undergo severe and con- 

 tinued exertion, more urea is secreted than in the most 

 highly fed individual, if in a state of rest.. In fevers 

 and during rapid emaciation the urine contains more 

 urea than in the state of health. (PR OUT.) 



32. In the same way, therefore, as the hippuric acid, 

 present in the urine of the horse when at rest, is con- 

 verted into benzoate of ammonia and carbonic acid as 

 soon as the animal is compelled to labor, so the uric 

 acid disappears in the urine of man, when he receives, 

 through the skin and lungs, a quantity of oxygen suffi- 

 cient to oxidize the products of the transformation of 

 the tissues. The use of wine and fat, which are only 



