If in this liquid the nitrate was replaced by an ammonium salt, the result was 

 quite the same. 



Secondly, the bicarbonate was replaced by common natrium carbonate, the same 

 quantities of the different salts being used. But in this case the action proved rather 

 injurious than favorable. It is true that the film had become considerable after a few- 

 months, but it was directly to be seen that the growth was so much inferior to that 

 of cultures obtained in the same circumstances but in absence of carbonate, that the 

 determination of the permanganate number seemed superfluous. Here, too, the re- 

 placing of nitrate by an ammonium salt or by a nitrite caused no change. 



As a remarkable fact it may be mentioned, that in these experiments, in our large 

 flasks, containing a litre of air, the thin bacterial film mounted very high up the 

 dry glass-wall, which is likewise often observed in the solutions made with distilled 

 water, and may repose on the absence of dissolved lime salts. 



If the tap-water was substituted by distilled water, the addition of natrium car- 

 bonate did not cause an increase of bacterial growth either. We found, for in- 

 stance, in: 



Distilled water 100 



KgHPOi 0.02 



(NH,)*SOi 0.02 



NaaCCh o.i 



Mineral solution* I drop 



after 7 months (5 May i Dec.) 155 mgrs. of permanganate, corresponding with 

 ca. 300 mgrs. of dry bacterial substance per litre, which production is less than that, 

 obtained in other cases under the same circumstances but without carbonate, so that 

 here also, the action of the carbonate, the long time of cultivation being taken into 

 consideration, was not favorable. Quantities of carbonate, smaller than 0.1% were 

 neither successful. 



The results of this examination can be thus summarised, that for the growth of 

 B. oligocarbophilus an atmospheric carbon compound is actually consumed, but that 

 this cannot possibly be free carbonic acid. Furthermore, that also combined carbonic 

 acid cannot serve for its nutrition. 



7. Nature of the assimilated atmospheric carbon compound. 



If the carbonic acid of the air cannot be the food of B. oligocarbophilus, what 

 other atmospheric carbon source might then come into consideration? 



It is clear, that we should think here of the carbon-containing component of the 

 air, discovered in 1862 by the botanist Hermann Karsten 1 ), and recently dis- 

 covered anew by French experimenters, especially by Mr. H e n r i e t 2 ). It is true 

 that the chemical nature of this substance has been hitherto unknown 3 ), but yet it is 



*) H. Karsten. Zur Kenntniss des Verwesungsprocesses. Poggendorffs Annalen 

 Bd. 191, pag. 343. 1862. To this place, as also to the not unimportant older literature 

 on the carbon compound of the air, my attention was drawn by Mr. G. van Iterson. 



-) Comptes Rendus T. 135, pag. 89 et 101. 1902. 



s ) Henriet thinks that the substance must be a monosubstituted formamid with 

 the formula HCO.NHR, where R represents a still unknown alkvlrest. But then it is 



