154 ASPAKAGIN. 



are dextrorotatory. It may be prepared synthetically, 1 but is 

 usually obtained by crystallisation from the expressed juice or 

 extracts of the seedlings of peas, beans, or lupins. 2 Mercuric 

 nitrate yields a precipitate with aspardgin which may be used for 

 its separation from vegetable extracts. 3 Urea-ferment converts it 

 into succinic acid. 4 



One point of interest with respect to asparagin remains to be 

 briefly mentioned. Seeing that in plants the nitrogen requisite 

 for the construction of proteids appears to be obtained largely 

 from asparagin, is there any evidence that in animals also the 

 nitrogen of this substance can take the place of that of proteids ? 

 The answer to this question may be stated as follows: When 

 asparagin is administered to carnivora or birds practically the 

 whole of it is converted into urea or uric acid respectively. 5 Thus 

 in carnivora at least there is no diminution of proteid metabolism, 

 such as is observed under a gelatin diet, when asparagin is added 

 to the food. In herbivora on the other hand there appears to be 

 somewhat distinct evidence that a part of the nitrogen in proteids 

 may be replaced by that of asparagin. 6 



The question as to the importance of the nitrogen of asparagin as a 

 possible replacer of that of proteids arose first in connection with the 

 dispute already referred to (p. 122) on the mode of formation of fats in 

 the animal body. In the experiments of Weiske and Wildt 7 on which 

 Voit chiefly based his original views, a diet of potatoes was largely 

 used. The amount of proteid in these was calculated from the total 

 nitrogen they contained, on the assumption that there was no nitrogen 

 present in them in any form other than that of proteids. As a matter 

 of fact potatoes contain a not inconsiderable quantity of asparagin, 8 so 

 that making allowance for this the total amount of proteid given in 

 their experiments was much less than they supposed, and might not 

 have sufficed to account for the fat stored up. This difficulty would 

 obviously be got over if it could be shown that the nitrogen of asparagin 

 can play the part of the nitrogen of proteids. 



1 See recently Piutti, Chem. Centralb. Bd. xtx. (1888), S. 1459. 



2 Piria, Ann. de Chim. et de Phys. (3) T. xxn. (1847), p. 160. Schulze u. 

 Bosshard, Zt.f. phi/siol. Chem. Bd. ix. (1885), S. 420. 



3 Schulze, E., Ber. d. d. chem. Gesell. 1882, S. 2855. 



4 Bufalini, Ann. di chim. e di farmac. (4) T. x. (1889), p. 207. 



& Von Knieriem, loc. cit. But cf. von Longo, Zt. f. phusiol. Chem. Bd. i. (1877), 

 S. 213. 



6 Weiske, Zt.^f. Biol. Bd. xx. (1884), S. 277. Weyl, Biol. Centralb. Bd. n. 

 ( 1882-83), S. 277. These give copious references to literature up to date. In 

 addition see Voit, Sitz. d. Bai/r. Akad. 1883, S. 401. Rohmann, Pfluger's Arch. Bd. 

 xxxix. (1886), S. 21. (On storage of glvcogen.) 



' Zt.f. Biol. Bd. x. (1874), S. 1 



8 Schulze u. Barbieri, Landwirth. Versuchs-Stat. Bd. xxi. (1877), S. 63. 



