10 



DE. BASTIAN ON THE 



The explanation of this fact is probably to be found in the sup- 

 position that, in starting the fermentation of some fluids, diminu- 

 tion of pressure may be of as much or even of more importance 

 than contact with free oxygen. This appears to hold good for hay- 

 and turnip-infusions. "With some other fluids the influence of 

 oxygen seems to be decidedly more potent as a co-initiator of fer- 

 mentation than that diminution of pressure which is brought about 

 by hermetically sealing the vessel before the fluid within has 

 ceased to boil. Urine is an example of this latter class. 



Fig. 1. 



Ketort with platinum electrodes. 



I have made only a few experiments bearing upon the effect of 

 adding oxygen to boiled urine contained within retorts from which 

 air has been expelled ; but to these I now refer, partly because 

 of the nature of the results obtained, though principally because 

 I shall be able to call the attention of other investigators to a 

 method which may hereafter prove capable of throwing much 

 additional light upon the conditions favouring the fermentation 

 of other boiled fluids, and perhaps upon the morphological varia- 

 bility of ferment- organisms — since it enables us at will to modify 

 the constitution of the fluid and the pressure to which it is sub- 

 jected, whilst we also expose it to varying amounts of oxygen. 



In order to ascertain the effect of the addition of oxygen gas 

 to boiled urine contained in a sealed vessel from which air has been 

 expelled by boiling, I have made use of a retort (fig. 1), into the 



