CONDITIONS OF LIFE OF THE FISSION FUNGI. 531 



Nencki convinced himself that in the cultivation appara- 

 tus ferrocyanideof iron and reduced haemoglobin remained 

 unaltered, and that thus we had to do with complete 

 absence of oxygen so far as this can be confirmed by 

 chemical means. 



Nageli has drawn especial attention to the great im- Replacement 



. . , - ,. ,. ., . f of the oxygen 



portance of the fermentative activity in reference to the by the 



need for oxygen on the part of the fission fungi; tf 

 fermentative action is going on the access of oxygen 

 becomes unnecessary ; if the bacteria in question are 

 unable to excite fermentation, or if it so happens that 

 they live under conditions in which no active fermentation 

 can occur, free oxygen becomes absolutely essential for 

 their development. 



Engelmann has further shown that the motility of i n fl uence of 

 the bacteria is influenced to a very great degree by the oxygen on 



., , . -,. tt 'ii movement. 



tension of oxygen in the nutrient medium. Spirilla are in 

 this respect much more sensitive than any other species 

 of motile bacilli ; the latter assemble at the margin of 

 any air bubble which may be present within a drop 

 of nutrient fluid; spirilla, on the other hand, remain 

 at some distance from the margin of the air bubble, 

 and only approach it when the amount of oxygen 

 in the nutrient solution has become diminished. In 

 this species of bacteria too great a quantity of oxygen 

 has also a similar effect in causing the cessation of 

 movement. The lower limit of necessary oxygen was 

 very low in this species of spirilla ; if they were placed, 

 along with micro-organisms containing chlorophyll, in 

 a medium which was free from oxygen but illuminated 

 with white, red, or yellow light, the spirilla. at once 

 collected at those parts where traces of oxygen were 

 developed by the chlorophyllous cells. 



More recent investigations by Liborius* have added to 

 our knowledge as regards the need for oxygen by the 

 bacteria, and have more especially shown that the 

 anaerobic organisms can live and multiply without 

 exercising any simultaneous fermentative activity. 

 According to Liborius' investigations we may divide the 



* Gott. hyg. List. See Zeifschr.f. Hygiene, vol. i. 



