The Presiclenfs Address. By H. J. Slack. 121 



on in the French Academy. Schiitzenberger, in his work on Fer- 

 mentation, says, " Yeast sets up alcohoHc fermentation in a solution 

 of pure sugar in the absence of all trace of oxygen, but without 

 developing ; this is contrary to the affirmation of M. Pasteur that 

 fermentation is bound up with the organization of the yeast, or is 

 a phenomenon correlative to the vital activity of the cells." 



Full explanations on this point are given by M. Pasteur in ' La 

 Biere.' I will cite one passage (p. 239), in which he says, " In order 

 to multiply itself in a fermentable medium, without the presence of 

 oxygen gas, the cells of yeast must be extremely young, full of life 

 and health, still under the influence of the vital activity they owe 

 to the free oxygen which assisted to form them, and which perhaps 

 they have stored up for a time. When older they have much 

 difficulty in reproducing themselves without air, and they age 

 more and more quickly : if they continue to multiply, it is under 

 a bizarre and monstrous form. When still older they remain 

 absolutely inert in a medium deprived of free oxygen. It is not 

 that they are dead : usually they rejuvenesce rapidly if sown in the 

 same hquid after it has been aerated." 



The lines of inquiry suggested by M. Pasteur may lead to 

 many valuable results. It is obvious that the chemist can compose 

 a great variety of nutrient fluids in which many of the lower 

 organisms can be grown. Certain mineral matters, compounds of 

 ammonia to supply nitrogen, and hydrocarbons that may be varied 

 to almost any extent, ofl'er the means of experiments presenting 

 different conditions and likely to lead to different results. 



Unless new methods can be devised, it will evidently be a waste 

 of time to seek amongst the simplest organisms for any transition, 

 or change of dead matter into living matter without the inter- 

 vention of a living cell ; but as the highest organisms are orderly 

 and co-ordinated aggregations of simple ones, the smallest living 

 particle capable of growth, reproduction and decay, may, when 

 rightly questioned, elucidate some of the profoundest problems with 

 which the biologist has to deal. 



