I 



. THE COMPOSITION OF THE URINE 1087 



acids. ^ This is true to a large extent, because even the body attempts 

 to remedy this defect by caUing to its defense first its reserves of 

 sodium and potassium and lastly, and most effectively, large quantities 

 of ammonia. We have seen that the proteins turn their effete nitrogen 

 into ammonium carbonate and carbamate which are then converted 

 into urea in the liver. When the body employs this ammonia as a 

 defense, it combines it with the diacetic and jS-oxybutyric acids and 

 does not convert it into urea. Consequently, the ammonia escapes in 

 this case into the urine as ammonium diacetate and ammonium 

 /3-oxybutyrate. Finally, when the body has reached its limit in this 

 regard, the normal alkalinity of the blood can no longer be maintained 

 and dyspnea, collapse and coma result. 



Creatin and Creatinin (C4H7N3O). — On a diet free from meat, 

 creatin is excreted in amounts varying between 7 and 11 mgr. per 

 kilogram of body weight. Folin^ regards it as a criterion of the inten- 

 sity of the endogenous nitrogenous metabolism and believes that" it is 

 formed in the liver and not in the muscles which usually contain it 

 in abundant amounts. Any gross variation from the amount just 

 given signifies an accumulation of this substance in the blood. Mel- 

 lanby claims that creatinin is derived from certain . derivatives of 

 protein catabolism in the liver and is then conveyed from this organ 

 to the muscles, where it is converted into its anhydride, creatin. As 

 soon as this tissue becomes saturated with this substance, creatinin 

 is excreted in the urine, and hence, a renal deficiency would invariably 

 be followed by an accumulation of the latter in the blood. 



Uric Acid (C5H4N4O3). — The quantity of uric acid normally present 

 in the urine of man is small. It varies between 0.3 and 1.2 grm. per 

 day or between 0.02 to 0.10 per cent. This amount may be derived 

 from the ordinary purin metabolism of the body (endogenous) or from 

 the food ingested (exogenous). For this reason, it may readily be 

 increased by the ingestion of food rich in nucleins, or substances 

 containing the purin bases in a free state. Since the human body 

 does not possess the power of destroying any of the uric acid, it must 

 be excreted as such in the urine. This being the case, one of the 

 earliest symptoms of renal insufficiency is the increase of uric acid in 

 the blood. The reason for this is not quite clear, unless it is taken 

 into account that its salts are the least soluble of any excreted in the 

 urine. This also explains the fact that urine when cooled, yields a 

 pink deposit of urates. Uric acid is present in large amounts in the 

 urine of birds and snakes, forming here acid ammonium urate. 



The purin bases are largely transformed into uric acid and only 

 their residue appears in the urine. Only traces of hippuric acid are 

 present under normal conditions (0.7 grm. per day), but the ingestion 

 of fruits and vegetables may raise it to 2 grm. per day. Amino-acids 



1 Von Noorden, "Diabetes Mellitus," Wright and Sons, Bristol, 1906. 



2 Am. Jour, of Physiol., xiii, 1905, 66 and Jaffe, Zeitschr. fur physiol. Chemie., 

 xlviii, 1906, 430. 



