THE NITROGENOUS EXCRETION. URINE. 361 



others. In addition to these four nitrogenous bodies several 

 others are known to be present in very small amount; their 

 consideration would not affect the relations given appreciably. 

 But in the last few years a new urine acid has been described 

 by several writers, and especially by Bondzynski and Gottlieb, 

 under the name of oxyproteic acid, which appears of more 

 importance. This substance, to which the formula 



was given, but not definitely proven, is very soluble and hard 

 to separate or recognize. Hence the fact that it so long es- 

 caped notice. According to the authors mentioned it is ex- 

 creted to the extent of 3 to 4 grams daily. Its nitrogen would 

 therefore make up 2 to 3 per cent of the total nitrogen ex- 

 creted, and if included would modify somewhat the above 



proportions. 



AMMONIA. 



This represents a portion of the protein disintegration 

 which for a number of reasons has not been converted into 

 urea. The ammonia passing into the urine takes that course 

 ordinarily through combination with mineral or other acids 

 which are not destroyed or may not be destroyed by oxida- 

 tion. In any pathological increase of such acids, if there is 

 not enough fixed alkali in the blood to combine with them, 

 ammonia is split off from protein derivatives in quantity suf- 

 ficient to complete the neutralization. This may be shown 

 also by the injection of free mineral acids either directly or 

 with the food; an increased elimination of ammonia results. 

 It should be expected therefore that the proportion of am- 

 monia in the urine would be subject to marked fluctuations, 

 which is indeed the case. Taken with other determinations 

 the estimation of ammonia may possess considerable diagnos- 

 tic value, as it measures to some extent the excessive acid 

 excretion. 



Ammonia must be determined in fresh urine only, since in 

 old urine fermentation changes soon produce large quantities 

 of the substance from the breaking down of urea. 



