IN SACCHAROMYCES. 11 



some of its symmetry, and the process of multiplication will 

 recommence and will continue according to the suitability of the 

 cultivating medium. We find, then, that in solutions containing 

 carbo-hydrates alone, the cell is scarcely able to survive, and its 

 power of propagation is lost ; while m media containing nitrogen 

 compounds the opposite conditions generally maintain. 



The next step is to learn something of the character of the 

 nitrogenous matters which produce this effect. It has been seen 

 that crystalloid nitrous compounds are capable of sustaining the 

 vitality of the cell, and that organic liquids, such as malt 

 infusions, are equally or better suited to the same purpose. It 

 remains, then, to ascertain whether, if any crystalloids present in 

 the organic infusions be removed, the liquid will still be as 

 capable of sustaining life. The writer first experimented with 

 liquids containing nitrogen in uncrystallisable form only, but 

 although the results were fairly definite, the method seemed 

 scarcely so satisfactory as cultivating in an organic infusion from 

 which crystallisable nitrogen could be removed. In order to do 

 this, a malt infusion was submitted to the action of a dialyser, 

 under suitable precautions, to prevent putrefactive or fermentative 

 changes, and the crystalloids were thus almost entirely abstracted 

 from the liquid. Comparative experiments were at the same time 

 made on liquids having a known amount of nitrogen crystalloids 

 of as nearly as possible a similar character. 



With proper precautions, cultivations were attempted in the 

 dialysed liquid, and on the second and third days the deposited 

 cells were examined. The appearances presented were closely 

 analogous to those of cells grown in solutions of sugar only, 

 although scarcely so definite. An attempt to carry the cultivation 

 further was unsuccessful, owing to the difficulty of avoiding putre- 

 factive changes, but enough was gained to indicate that the 

 withdrawal of the crystallisable nitrogen rendered the liquid unfit 

 to maintain the vitality of the cells for any time. 



To investigate the precise nature of these nitrogen bodies 

 would involve chemical research beyond the limits of the present 

 article. The writer is inclined to think that when such research 

 is undertaken it will be found that compounds of an amide 

 character play an important part, and that the suitability of a 



