AMMONIA. 585 



According to Tschlenoff, 1 if the urea excretion after a meal rich in 

 proteids be estimated from hour to hour, it will be found to exhibit two 

 maxima: The first occurs at the third or fourth hours, and the second at 

 the sixth or seventh. These he considers to indicate the absorption of 

 peptones from the stomach and intestine respectively. If peptones be 

 given instead of ordinary proteids, the maximum is reached by the second 

 hour. Mares, 2 on the other hand, found that after an isolated meal the 

 maximum of urea excretion was not reached till the ninth hour. 

 Kobler 3 has found that simple diuresis under normal circumstances is 

 not accompanied by increased excretion of urea. 



(c) Ammonia. The urine of man and of carnivorous animals 

 invariably contains small quantities of ammonium salts. They may 

 be absent, however, from that of herbivora. The quantity in human 

 urine is about 0'7 grm. NH 3 per diem ; the variations in health extend- 

 ing from about 0'3 to 1*2 grms. 4 



The ingestion of ammonium carbonate, or of organic ammonium 

 compounds susceptible of oxidation in the body, does not increase the 

 excretion of ammonia, for the nitrogen of such compounds is excreted 

 wholly as urea. If, however, stable salts of ammonium, such as the 

 chloride, are given, they appear (in the case of carnivora, at any rate) as 

 such in the urine. 



Apart from such direct ingestion of stable ammonium salts, the 

 excretion of ammonia depends almost entirely upon that question of 

 adjustment between acid production in metabolism and the supply of 

 bases in the food which was discussed in the section devoted to the 

 acidity of the urine (q.v.). Ammonia formation is the physiological 

 remedy for deficiency of bases. 



When acid production is excessive (a condition especially seen in 

 certain forms of diabetes), or when mineral acids are given by the 

 mouth, the urinary ammonia increases at the expense of the urea. 

 When the bases are in excess, whether from the nature of the food or 

 from the administration of alkalies, the ammonia disappears, and a corre- 

 sponding amount of urea is excreted in its place. From this it follows 

 that little or no ammonia is found in the urine of herbivora ; and that, 

 in man, flesh food raises the quantity, and vegetable food diminishes it. 5 



From the abundance of bases in their food, it is very difficult, by any 

 means, to increase the urinary ammonia of herbivora. If, for example, 

 abundant ammonium chloride be given to a rabbit, together with a normal 

 supply of vegetable food, its urinary ammonia is but little increased. 6 By 

 double decomposition with sodium carbonate in the tissues, ammonium car- 

 bonate and sodium chloride are formed, and the former is excreted as urea. 



It would seem that the organisation of the herbivora does not permit of 

 a supply of ammonia to neutralise acids when given in excess. Thus, most 

 herbivorous animals are said to be much more susceptible to poisoning by 

 acids than are the carnivora. 



1 Abstract in Centralbl. f. Physiol., Leipzig u. Wien, 1896; cf. also Veragutt, Journ. 

 Physiol., Cambridge and London, 1897, vol. xxi. p. 112. 



2 Jahresb. u. d. Leistung. . . . d. ges. Med., Berlin, 1887, Bd. i. S. 145. 



3 Wien. Tclin. Wchnschr., 1891, Nos. 19, 20. 



4 Neubauer, Journ. f. prakt. Chem., Leipzig, 1852, Bd. Ixiv. S. 177. These figures are 

 confirmed by numerous later observers. 



5 Salkowski and Munk, Virchow's Archiv, 1877, Bd. Ixxi. S. 500 ; also Gumlich, 

 Ztschr.f. physiol. Chem., Strassburg, 1893, Bd. xvi. S. 19. 



6 E. Salkowski, Ztschr. f. physiol. Chem., Strassburg, 1877, Bd. i. S. 26. 



