102 UREA. HIPPURIC ACID. AMINOACIDS 



whole group of studies may be briefly condensed into the 

 statement, that the liver can be practically excluded 

 without abolishing or in any marked degree reducing the 

 formation of urea. It is true that in these subjects 

 there sometimes occurs a lowering of the urea (from 90 to 

 75 per cent, of the total nitrogen), with corresponding in- 

 crease of ammonia (the latter increasing from about 3 to 5 

 per cent, of the total nitrogen to 20 per cent, or more) . But 

 on the other hand it is known that loss of hepatic function 

 coincides frequently with an " acidosis," that is, with ac- 

 cumulation of acid metabolites ; and it is not at all unreason- 

 able to think that this may very satisfactorily explain the 

 diminution of urea formation and coincident ammonia in- 

 crease (v. inf.). In dog fish, in the tissues of which there is 

 an unusually large proportion of urea, it has not been pos- 

 sible to reduce this by extirpation of the liver. 7 Eecent clin- 

 ical observations have invariably indicated that ammonia 

 elimination is very commonly heightened in severe liver 

 affections, although scarcely more than in fever or in con- 

 ditions of acidosis ; and it is altogether impossible to con- 

 clude that observation of urea-ammonia-elimination affords 

 a safe basis or deduction as to the hepatic function. 8 



Generally speaking, the inclination at the present time 

 is increasingly toward the belief that the ability to form 

 urea is by no means confined to the liver, but is one of the 

 common characteristics of all living cells, just as is the 

 power of protein combustion. In very low types of life, in 

 fact, urea does not appear as such in the excretory products ; 

 instead we find uric acid, which may be conceived as built up 

 of two molecular urea rests and one tri-carbon group. 9 



Y W. v. Schroeder, Zeitschr. f. physiol. Chem., 14, 576, 1890. 

 W. Frey (Gerhardt's Clinic, Basel), Zeitschr. f. klin. Med., 72, 383, 1911. 

 Literature upon Excretion in Lower Animals: O. v. Flirth, Vergl. chem. 

 Physiologic d. nieder. Tiere, Jena, 1903. 



