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 bo exhibit two 
maxima. The first occurs atthe 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 of dinary 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 horn*. 
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 ■07 grm. NH 3 per diem; the variations in health extend- 
ing from about 0*3 to 1*2 grins. 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. 
Abstract in Centralbl. f. Physiol., Leipzig u. Wien, 1896; cf. also Veragutt, Journ. 
Physiol., Cambridge and London, 1897, vol. xxi. p. 112. 
2 Jahresb. ii. d. Leistung. . . . d. ges. Med., Berlin, 1887, Bd. i. S. 145. 
3 Wien. klin. Wchnschr., 1851, Xos. 19, 20. 
4 Xeubauer, Journ. f.praU. Chem., Leipzig, 1852, Bd. lxiv. S. 177. These figures are 
confirmed by numerous later observers. 
5 Salkowski and Munk, Vvrchow's Archiv, 1877, Bd. lxxi. S. 500 ; also Gunilicli, 
Ztschr.f. physiol. Chem., Strassburg, 1893, Bd. xvi. S. 19. 
6 E." Salkowski, Ztschr. f. physiol. Chem., Strassburg, 1877, Bd. i. S. 26. 
