216 LECTURE X. 



made that this substance acted differently in the organisms of the car- 

 nivora than in that of the herbivora. With the former and with the 

 omnivora, asparagine cannot be utilized as a substitute for albumin; but 

 this substance does act as an albumin-sparer with the herbivora. It is 

 not easy to interpret this result. We cannot exactly realize how asparagine 

 can act as a substitute for albumin. It is, of course, possible, in fact 

 very probable, that the animal organism is capable of forming one amino 

 acid at the expense of another; we cannot, however, believe it possible 

 to produce albumin from asparagine alone. Such an assumption is entirely 

 out of the question. It seems more probable that it is active in another 

 direction. It has been thought that the asparagine in the intestines pro- 

 tects the albuminous material of the food, before disintegration, against 

 the attacks of micro-organisms; in fact, it has even been suggested that 

 the bacteria in the intestines synthesize albumin from asparagine, which 

 is then absorbed by the organism. It is interesting to note that ammo- 

 nium acetate l and succinamide 2 are credited with having the same effect 

 as that of asparagine. We cannot consider this question as solved, from 

 the investigations at hand; only this much is certain, that asparagine can- 

 not be looked upon as a substitute for albumin in the sense that gelatin 

 is. Its action is an indirect one. 



In this connection we may state that the lower forms of life, like the 

 molds, can utilize an individual amino acid as a starting-point in the 

 synthesis of albumin. This is not so remarkable, for, if the nitrate- 

 nitrogen is available, then the amino acid-nitrogen ought also to be of 

 value. Experiments with Aspergillus niger 3 indicate that, within certain 

 limits, the production of albumin is entirely independent of the source of 

 the nitrogen. This mold synthesized its albumin just as efficiently in 

 a potassium nitrate medium as when it was supplied with glycocoll or 

 glutaminic acid as its sole source of nitrogen. Furthermore, the exam- 

 ination of the albumin in the mold showed it to be composed of apparently 

 the same relative amounts of individual amino acids in all three experi- 

 ments. Glycocoll, alanine, leucine, glutamic acid, and aspartic acid were 

 all obtained from the mold. This phenomenon might be explained by 

 assuming that this mold evidently decomposes the amino acids presented 

 as nutriment, i.e., possibly splits off the amino group, and starting from 

 ammonia begins the synthesis anew. In the same manner it probably 

 produces the same substances from the nitrates, and eventually forms 

 most complicated compounds. Czapek 4 and O. Emmerling 5 have already 



1 O. Kellner: Z. Biol. 39, 339 (1900). 



3 Weiske: Z. Biol. 20, 279 (1884). 



8 E. Abderhalden and P. Rona: Z. physiol. Chem. 46, 179 (1905). 



4 F. Czapek: Hofmeister's Beit. 1, 542 (1902). 



5 O. Emmerling: Ber. 35, 2289 (1902). 



