544 Adeney — Dissolved Gases and Fermentative Changes. 



stages, even in the continued presence of free oxygen, and that in the first stage 

 the organic substance is simply broken down, the carbon and nitrogen, if present, 

 being convei-ted largely into carbon dioxide and ammonia, a small quantity of 

 organic matter, however, remaining as such, but in an altered form ; that in the 

 second stage the ammonia is oxidized to nitrous or nitric acids, or both, and 

 that, at the same time, the organic matters resulting from the first stage may 

 be partially or completely oxidized, carbon dioxide and possibly nitric acid being 

 formed ; — also that the second stage does not commence until the completion of the 

 first. I shall call these two "first" and "second" stages of fermentation for 

 want of better terms ; new terms are, in fact, wanted to describe them properly. 

 My friend Dr. E. A. Letts has suggested to me a term which seems to be very 

 suitable for the first, viz. bacteriolysis. 



Method of Experimenting. 



In considering this question, three conditions which the method adopted would 

 be required to fulfil had to be borne in mind : — 



1. It should not be possible for any gas, during an experiment, to gain access 

 to, or egress from, the vessel in which the experiment was to be carried on. 



2. It should be possible to easily and accurately regulate the quantities of 

 dissolved oxygen and of fermentable matters, relatively to one another in a liquid 

 to be examined, so that the former should be in excess of the latter, or vice versa, 

 just as required. 



3. The external conditions of a liquid during fermentation should be similar 

 in all respects, and such as to ensui-e, as far as practically possible, that every part 

 of the liquid throughout its mass should be chemically similar at any interval of 

 time during the continuation of the experiment.* 



These necessary conditions made it impossible for me to use the method of 

 liquid cultivations, as commonly employed by bacteriologists, viz. nutrient liquid 

 media, in which the relative quantities of fermentable matters and dissolved 

 oxygen are not specially regulated, and which are kept in bottles or in flasks, 

 which they only partially fill. 



With such a method it would be quite possible, as bacteriologists have generally 

 observed, to have a fermentation in the continued presence of an excess of atmo- 



" In connection with this point, see Dr. P. F. FrankLand and Mr. Frew's very interesting experi- 

 ments, described in their Paper on "A Pure Fermentation of Mannitol and Dulcitol." — C. S. J., 61, 

 p. 254. 



