action of alkali, gives out as much carbonic acid as occurs already in a free state in 

 the same volume of air, that is per litre 0.3 cM 3 . = 0.6 mgrs. in which 0.163 rngrs. 

 of carbon are pesent. Thus, for 8.8 mgrs. are wanted 55 litres of air. Consequently, 

 in the course of a month these 55 litres of air must have diffused through the cotton 

 plug inward and outward of our K litre-flasks, in order to produce the found quantity 

 of carbon, that is 76 cM 3 . hourly. 



Though this figure should not be considered a priori as impossible, it still appears 

 to be very high, and the difficulty of accepting it increases, if still the addition has 

 to be made of a yet unknown, but apparently considerable amount consumed for the 

 bacterial respiration, which, as remarked above, seems necessary. We therefore think 

 that it must be admitted that the quantity of the atmospheric compound (or com- 

 pounds) assimilable by B. oligocarbophilus, is much larger in our laboratory atmo- 

 sphere, than in that of the Paris boulevard, analysed by H e n r i e t, and that we have 

 here to do with an extremely variable factor. The circumstance, too, that we have 

 not as yet been able in our greenhouse, where the air, in the common sense of the 

 word, is surely much purer than in the laboratory, to obtain a vigorous growth of B. 

 oligocarbophilus pleads for this view. But here we could not always keep the tem- 

 perature high enough, so that we consider our experiments in this direction not yet 

 closed. Besides, we should observe, that in an empty, isolated room of the laboratory; 

 the quantities of combined carbon drawn from the air, were as great, or only little 

 less than in the laboratory itself, where the air was certainly impurer. 



We are accordingly conscious that further experiments, with fresh atmospheric 

 air are wanted to decide, whether the carbon compound occurs in the atmosphere in 

 a constant or in a varying percentage. Only thereby it will be possible to ascertain the 

 distribution of this compound, by which, at the same time, the signification of B. 

 oligocarbophilus in nature will become clearer. 



As to this signification, the question arises whether our microbe in substrata 

 containing sufficient mineral nutrients (N, P,- K, Mg, S, Fe, Mn), but being poor in 

 organic substances, is able to build up the latter in the dark from the volatile carbon 

 compounds occurring in the atmosphere of the surrounding medium. And furthermore, 

 whether carbon nutrition takes place exclusively in the floating dry films, - - hence, in 

 the earth, only on the relatively dry surface of the earth particles, - - or that also in 

 the depth of fluids growth and carbon assimilation be possible. The hitherto gathered 

 experience about the self-purification of rivers and the biological purification of water 

 in general, seems to exclude the latter hypothesis, and our own experiments too, 

 render it not probable. The result of these experiments consists, in our opinion, in 

 the very discovery of a microbe, which, in consequence of the film-formation, has the 

 specific faculty, to absorb for its nutrition and multiplication, from a gas, namely the 

 air, traces of volatile carbon compounds, by which the struggle for existence with the 

 rest of the microbic world can be successfully sustained. The biological purification 

 of water would, according to this view, find a counterpart in the biological purification 

 of the air by Bacillus oligocarbophilus. 



