( 1«' ) 



If it is accepted that this relation holds also ^ood for the obli- 

 gatuus anaerohica, then it is to be expected that their provision of 

 oxygen will be much smaller than that in the yeastcell, so that it is 

 necessary to take much more efficacious measures to render the 

 influence of the oxygen visible in the former than in the latter case. 

 It is therefon; desirable, in some cases even necessary, to use for 

 the experiments materials, taken from such cultures as have long 

 been continued in absence of air, by which the provision of oxygen has 

 been lessened. So far as I am now able to judge, strongly aerated 

 anaërobics are, as to their growth, acrophobic, i. e. they grow best 

 there where the oxygen tension is minimum or zero. As contact 

 with air is in itself not sufficient to cause aeration, — spores for 

 instance seem less fit to be aerated than vegetative cells, — there 

 now and then occur strange incidents which make the experiments 

 troublesome. 



The way in which I arranged my growth experiments is as follows. 



Material of the species to be examined, is introduced, in a not 

 aerated condition, and. if possible, in the state of spores, into the 

 culture mass still iu fusion, in such a quantity, that the germs, 

 developped into colonies, may render that culture mass, after solidi- 

 fication, rather opaque. 



If such a culture mass, from which the free oxygen is completely 

 withdrawn, is contained in a deep experiment-tube, where the air 

 can only find access from above, then, if the growth is favoured by 

 a certain oxygen tension, there must result at the very place where 

 this tension becomes optimum, an opaque and distinctly visible 

 niveau of colonies, which are greater than the colonies beneath and 

 above this niveau. 



The easiest way for completely removing the oxygen, is to 

 sow simultaneously an acrophilous species, not acting injuriously on 

 the development nor disturbing the observation of the anaerobic. 

 Such an aerobic must have the following qualities : The oxygen 

 must be completely absorbed, without exciting so much growth iu 

 the surface of the culture mass, that the colonies of the anaerobic 

 become indistinct. Besides, an easy recognition in the microscopic 

 preparation, and a simple separation of the aerobic and the anaerobic 

 must be possible. 



In trying various species of microbes, I found some kinds of 

 yeast to be most efficient for the research of the anaërobics of putre- 

 faction and of sulphate reduction, as for these processes no carbohy- 

 (iiales aic essential, in which case yeast does not grow strongly, 

 whilst it is distinctly recognisable under the microscope. Besides, 



