( n ) 



yeast can easily be separated from the anaiirobics of proteine putrefac- 

 tion, because it dies at 50° h 60° C, whilst the spores of the latter 

 can be heated to 90° a 100° C. without dying. For the examina- 

 tion of those anaërobics whicli require sugar in their food, as for 

 instance the butyric ferments, it is preferable, for oxygen absorption, 

 to make use of certain blastomycetes (which grow and reproduce 

 like yeast, whilst alkohol fermentation is absent) or aerobic bacteria, 

 which don't i)roduce acid, nor liquefy gelatine. Good results were 

 obtained with a red blastomycete, isolated from garden-soil, and with 

 Bacillus fliiorescens non liquefaciens. 



It is good (but not always necessary), to place the prepared 

 experiment-tubes, in an exsiccator which is vacuated. For this vacua- 

 tion a KoRTiNG-waterjetpump with manometer will suffice, by which 

 at the same time the pression of the gas used may be measured. 



Another very suitable method to state the influence of oxygen 

 on the growth, is to cultivate in the „humid room" on the object- 

 bearer under the cover-glass, in a not too small quantity of the 

 nutritious liquid, but in such a way as to keep the preparation 

 thin enough for the microscope. In this way it is possible to observe, 

 in the same preparation, first the figure of respiration and afterwards 

 the growth. 



The species of obligatous auacrobics which I have examined are 

 the following. 



Butyric ferment (Granulobacter sacclmrohuttjricuin). This anaci'obic 

 is extremely common in garden-soil. Fit material for figures of respir- 

 ation is to be obtained as follows. Water with some kalium phos- 

 phate and magnesium sulphate and 5 or 10 pCt. glucose is boiled 

 in a little flask with so much fibrine that a thick paste is formed. 

 During the boiling an infection with garden-soil is practised, in which 

 only spores of bacteria remain alive. In the thermostate a vegetation 

 of aerobics develops first, which, by the absorption of the oxygen, 

 introduces butyric fermentation. Sometimes this fermentation will follow, 

 even in absence of aerobics, i. e. notwithstanding the entrance of air into 

 the mass of fibrine, thus showing that some aeration is certainly no 

 bar to this process. If perhaps an aerobic grows too strongly, reinfection 

 in another flask with the same mixture, will suffice to make it dis- 

 appear and at length still to obtain an almost pare butyric fermen- 

 tation. If in the infection material there are too few spores, 

 as well of the butyric ferment as of aerobics, some aerobic bactery, 

 or a blastomycete must be purposely added for the absorption of 

 the oxygen. 



In this way a cukuie is obtained containing only the „oxygeu- 



2 



Proceediugs Royal Acad. Amaterdam. Vol. 1. 



