igo 



certain that we have here to do with an easily oxidisable compound (or compounds), 

 for a prolonged contact with alkali and air already suffice to split off carbonic acid 

 from it. Furthermore, according to the statement of the French investigator, the sub- 

 stance probably contains nitrogen. 



This latter circumstance gives rise to the question whether this nitrogen, like the 

 carbon, is fit for assimilation by our microbe. Though this question has already partly 

 been answered in the negative by the preceding experiments, it should still be remar- 

 ked here that in nutrient liquids, without an expressly added nitrogen compound, for 

 instance in: 



Distilled water 100 



K-.-HPO4 0.02 



Mg. S, Mn, Fe traces. 



Or still better in: 



Tap-water TOO 



K-'HPCh 0.02 



without any further addition, a not inconsiderable growth of B. oligocarbophilus 

 may occur, so that at least traces of an assimilable nitrogen compound may be drawn 

 from the air by this bacterium, whereas, for the possibility of assimilation of the free 

 atmospheric nitrogen no indications were found. 



We now turn to another question, which the assimilation of the atmosperic carbon 

 gives rise to, namely: How great is the quantity of the volatile substance wanted for 

 the formation of the bacterial film produced in our cultures? This question is closely 

 connected with the following: How much of the compound is moreover consumed 

 by the respiration of our bacterium, escaping as free carbonic acid? For answering 

 these questions we have to measure the quantity of the carbonic acid corresponding 

 with a determined weight of dry bacterial substance, granted that the carbon per- 

 centage of this substance be known. 



Our experiments relating to the measurement of the quantity of carbonic acid pro- 

 duced, are not yet closed, but as to the first part of the question, we give the following 

 calculation to fix the volume of air wanted for the production of the carbon, actually 

 accumulated in the bacterial films. We hereby make two chemical suppositions which, 

 to be sure, are fairly well in accordance with truth. First, we admit that the carbon, 

 freed from the unkown compound, as carbonic acid by a prolonged contact with alkali, 

 is consumed quantitatively by our bacterium and, secondly, that the bulk of the bac- 

 terial cells consists of a substance possessing nearly the composition of cellulose 1 ). 



Let us now consider the case when, in % litre-flask with TOO cM 3 . of fluid and 

 a free surface of 80 cM 2 , after a month's culture a quantity of 20 mgrs. of dry bac- 

 terial substance is formed, which, calculated as cellulose, contains 44% C.; we then 

 find in the 20 mgrs. of dry matter 8.8 mgrs. of carbon. According .to H e n r i e t the 

 atmospheric carbon compound, present in a certain quantity of air, under prolonged 



not easy to understand, why the production of carbonic acid takes place so readily. 

 It might then rather be expected that, with an alkali a formiate would result and no 

 carbonate. 



') If accepting that the composition of the bacterial cells corresponds with that 

 of albuminous substances, then, instead 44% C., 52 to 55% C. should be brought into 

 account, and in this proportion the volume of the air should be augmented. 



