ALBUMINS OR PROTEINS. 201 



stituents of table accessories. Concerning the relations which the purine 

 bases, and their accompanying intermediate products, bear to the 

 metabolism of albumin, nothing can be affirmed. It is, of course, 

 possible that they are derived from the nucleins. The alkaloids have 

 often been assigned a relationship to albumin. We know little about 

 their origin. It is possible that the dyestuff, indigo, is related to albumin 

 metabolism. In discussing the decomposition products of proteins we 

 met with tryptophane, skatole-amino-acetic acid, and have seen that 

 putrefaction decomposes this into indole, skatole, skatole-acetic acid, and 

 skatole-carboxylic acid. Skatole is rarely found in plants. The Japanese 

 wood, Ulmacace, Celtis reticulosa Miq., contains approximately 1 per cent 

 of skatole. Recent investigations also indicate the occasional appearance of 

 indoxyl among plants. We know nothing definite about the relations of the 

 indoxyl derivatives to the albumin decompositions in the plant organism. 



We are not much better informed concerning the processes participating 

 in albumin syntheses. The nitrates which the plant takes up must be 

 reduced. It is now usually assumed that the leaves are mainly instru- 

 mental in effecting the albumin syntheses; the idea being that amino acids 

 are first formed, which by recombining among themselves produce higher 

 complexes, and finally albumin itself. Although the leaves themselves are 

 incapable of utilizing the nitrogen of the air, as such, observations have 

 been made indicating that they can absorb small amounts of ammonia. 

 It seems that light has also an effect upon the production of albumin. 

 Albumin is, to be sure, formed in the dark, but the synthesis proceeds much 

 more rapidly in the sunlight. We are still entirely in doubt as to how 

 the amino acids are formed. We can assume, as previously indicated, 

 that they are derived from simple carbohydrates, for instance, from gly- 

 cerose; or we can just as easily imagine that the formation of the amino 

 acids is a more direct assimilation process. The manner in which the 

 nitrates are utilized presents a difficult problem. It is certain that they 

 must be reduced. The nitrite formation has also been followed directly. We 

 have assumed that HNOs goes over into HNO2, and this into HN : O. 

 The addition of water would produce hydroxylamine, NH 2 . OH, which, 

 in conjunction with formaldehyde, obtained by the reduction of carbonic 

 acid, produces formamide, HCO . NH^. 1 The formation of hydrocyanic 

 acid and the reduction of a nitrate to ammonia have also been suggested. 

 It is almost impossible at present to draw any positive conclusions. The 

 synthesis of albumin in the organism of plants, or, perhaps better stated, 

 the formation of the amino acids, as yet remains entirely unexplained. 



We have a better conception of albumin metabolism in germinating 

 seeds. Ripe seeds contain large stores of albumin. They, therefore, act 



1 A. Bach: Compt. rend. 122, 1499 (1896). 



