CHEMICAL BASIS OF THE ANIMAL BODY. 141 



which are easily soluble in water (1 in 4 -3), insoluble in cold, slightly 

 soluble in hot alcohol, insoluble in ether. 



Its solutions possess an acid reaction, but a sweet taste. Glycin 

 has also the characteristic property of uniting with both acids and 

 bases, to form crystallisable compounds, as also with salts. In this 

 it exhibits its amidic nature, which is further clearly evidenced by 

 the method of its synthetic production by the action of monochloracetic 

 acid on ammonia : 



CH 2 (Cl) . COOH + 2NH 3 = CH 2 (NH 2 ) . COOH + NH 4 Cl. 1 



Preparation. Either synthetically as above or more usually by the 

 decomposition of hippuric acid by prolonged boiling with hydrochloric 

 acid whereby it is split up into glycin and benzoic acid, the latter being 

 separated by crystallisation and shaking up with ether in which glycin 

 is insoluble. 



3. Sarkosin. C 3 H 7 N0 2 . [CH 2 . NH (CH 3 ) . COOH]. (Methyl- 

 glycin). 



Like glycin in its general chemical properties it further resembles it 

 in that it is never found in the free state as a constituent of the animal 

 body. It is however a substance of considerable interest and importance, 

 not merely on account of its chemical relationship to kreatin (see below) 

 but as having been employed in a well-known series of experiments in- 

 tended to elucidate the probable mode of formation of urea in the body. 

 It was stated that when sarkosin is administered to an animal in quan- 

 tities such that the nitrogen given as sarkosin is equal to the daily 

 output of nitrogen as urea by the animal, the urea disappears from the 

 urine and is replaced by a new substance 2 . The latter appeared to 

 be a compound of sarkosin and carbamic acid, known generally by 

 the name of methyl-hydantoic acid, NH 2 . CO . N(CH 3 ) . CH 2 . COOH. 

 This substance may be regarded as arising from the union of one 

 molecule of sarkosin with one of carbamic acid and elimination of one 

 molecule of water, or as being urea in which two atoms of hydrogen 

 are replaced by methyl and a residue of acetic acid respectively : 

 NH 2 . CO . N (CH 3 ) (CH a . COOH). The conclusions drawn from these 

 observations were that just as methyl-hydantoic acid is supposedly formed 

 by the union of sarkosin with carbamic acid and subsequent dehydration, 

 so also would urea be formed if, instead of sarkosin, ammonia were 

 present, to unite with the carbamic acid, form ammonium carbamate 

 (NH 4 . NH 2 . C0 2 ) and by loss of water yield urea. Subsequent repetition 

 of these ingenious experiments has shown that they are in no way 



1 Mauthner u. Suida, Monatshefte f. Chem. Bd. xi. (1890), S. 373. 



2 Schultzen, Ber. d. d. chem. Gesell. 1872, S. 578. 



