THEORY OP FERMENTATION 355 



have met with in which hydrogen was absent, there was no 

 formation of butylic alcohol. 



From a consideration of all the facts detailed in this sec- 

 tion we can have no hesitation in concluding that, on the 

 one hand, in cases of butyric fermentation, the vibrios which 

 abound in them and constitute their ferment, live without 

 air or free oxygen; and that, on the other hand, the pres- 

 ence of gaseous oxygen operates prejudicially against the 

 movements and activity of those vibrios. But now does 

 it follow that the presence of minute quantities of air ' 

 brought into contact with a liquid undergoing butyric fer- 

 mention would prevent the continuance of that fermenta- 

 tion or even exercise any check upon it? We have not 

 made any direct experiments upon this subject; but we 

 should not be surprised to find that, so far from hindering, 

 air may, under such circumstances, facilitate the propaga-? 

 tion of the vibrios and accelerate fermentation. This is ex- 

 actly what happens in the case of yeast But how could 

 we reconcile this, supposing it were proved to be the case, 

 with the fact just insisted on as to the danger of bringing 

 the butyric vibrios into contact with air ? It may be possible 

 that life without air results from habit, whilst death through 

 air may be brought about by a sudden change in the con- 

 ditions of the existence of the vibrios. The following re- 

 markable experiment is well-known: A bird is placed in a 

 glass jar of one or two litres (60 to 120 cubic inches) in 

 capacity which is then closed. After a time the creature 

 shows every sign of intense uneasiness and asphyxia long 

 before it dies; a similar bird of the same size is introduced 

 into the jar ; the death of the latter takes place instanteously, 

 whilst the life of the former may still be prolonged under 

 these conditions for a considerable time, and there is no 

 difficulty even in restoring the bird to perfect health by 

 taking it out of the jar. It seems impossible to deny that 

 we have here a case of the adaptation of an organism to 

 the gradual contamination of the medium; and so it may 

 likewise happen that the anaerobian vibrios of a butyric 

 fermentation, which develop and multiply absolutely without 

 free oxygen, perish immediately when suddenly taken out 

 of their airless medium, and that the result might be dif- 



