320 



for the process of putrefaction in general. I isolated various varieties and by means 

 of grovvth experiments I was enabled to state microaërophily. The mobility of my 

 varieties was too insignificant to be of use for the production of figures of 

 respiration. When using the above mentioned pepton gelatine as nutriënt matter and 

 Saccharomyces apiculatus for the absorption of oxygen, most convincing »niveaus«, 

 of a light brown color and with much growth, originate in deep experiment-tubes at 

 a certain distance from the surface, in the surface itself the transparent clear colonies 

 of the apiculatus-yeast develop vigorously, the skatolbacteria not being able to deve- 

 lop there. 



The spore-formation seems here also to be favored by a small quantity of oxygen. 

 Certain it is that spores are the most profusely formed in the niveau, and as their pro- 

 duction goes parallel, first to the weakening and then to the complete liquefying of 

 the gelatine, it is clear that also the latter process must begin in the niveau, to become 

 only much later perceptilile in the depth, and without reaching the surface at all. 



I vi'ish to terminate this survey of the obligatous aiiaërobics, studied by me, with 

 the statement that the existence of microaërophily could also be proved for Spirilluni 

 desulfuricans by means of growth experiments. 



This species is, in opposition to S. tenue, strictly anaërobic and belongs mor- 

 phologically to quite another group than the butyricferments and the bacteria of 

 putrefaction, which is clearly demonstrated as well by the vibrio- or spiril-form, as 

 by the absence of spores '). 



If sown in pepton gelatine, with Mohr's salt and an aerobic bactery {B. termo) 

 for the absorption of oxygen, in deep experimenttubes, the microaërophily becomes 

 visible by a black »niveau« of ferrosulfid, first formed at some distance beneath the 

 surface and thence, only slovvly, growing towards the depth and upward. When micro- 

 scopically examined this niveau proves to be richest in reducing spirilli, so that evi- 

 dently not the function of the sulphate reduction as such, but the growth of the 

 SpirUhiiii, active in this process, is furthered by a low oxygen tension. 



It is fit here to make a few remarks concerning the relation of facultative anaërobics 

 to free oxygen. By far the greater part of facultatives is aërophilous. I mention for 

 instance Miicor racemosiis, all alcohol yeasts, Bacteriutn coli commune, B. lactis 

 aërogenes, Granulobacter polyDiyxa. BaciUus tubcrciilosis, B. prodigiüsus. If the pro- 

 duction of figures of respiration is possible, then the width of the moving bacteria 

 zone is very great, even in dense swarms, which indicates a slow consumption of oxy- 

 gen. This is especially the case with the fermenting species, as coli and aërogenes, 

 and sometimens, too, with not fermenting species, such as BaciUus tuberculosis^). 



Microaërophilous are among the facultatives, so far as I think I can assert now, 

 only the true lactic ferments, which may be brought to two groups of which the most 

 important representativcs are: Bacterium lactis (of butterniilk), and BaciUus longus 

 (of cheese and of the yeast industry). 



As these forms have no motion and produce little living matter in growing, the 

 total quantity of absorbed oxygen is very sniall, whence the experiments are 



') As I tliiiik the only wcll-dcscribed instance of a sporc-frce obligatous anaërobic. 



') The mobility of BaciUus tuberculosis has first been seen by Mr. M acGilla vry. 

 The figures of respiration are troublesome to obtain and only with quite young cul- 

 tures, as for instance of flcsh bouillon agar, not older than 24 liours. 



