26 Chapter 1 



broth of the same composition but to which has been added the 

 filtrate from an unadapted culture, the bacillus does not develop 

 nearly so well. The difference is explained by the presence, in the 

 fluid in which the adapted bacillus had grown, of a certain quantity 

 of the mucous substance which fixes the arsenic and prevents it from 

 acting on the protoplasm of the micro-organisms. 



The Yeasts, also, adapt themselves very readily to antiseptics. 

 This property has even had a practical application. We know that 

 small doses of hydrofluoric acid are capable of preventing the 

 proliferation of the yeast of beer, and Effront 1 has accustomed this 

 plant to live in media containing an amount of hydrofluoric acid 

 which is absolutely inhibitory to the unadapted yeast. Under these 

 conditions the adapted cells undergo a stimulation which causes the 

 production of a greater quantity of alcohol. The yeast, in adapting 

 itself to antiseptic doses (300 mm. of hydrofluoric acid per 100 c.c. of 

 beer wort), acquires a kind of immunity which it did not possess in 

 the first instance. Moreover this acquired property can be hereditarily 

 transmitted to new generations developed in ordinary beer wort to 

 which hydrofluoric acid has not been added. The stimulating action 

 of this substance on the fermentative property does not depend upon 

 the acid reaction of the hydrofluoric acid, for other acids which are 

 [29] non-antiseptic, such as tartaric acid, are incapable of inducing it. 



The acquired immunity against hydrofluoric acid is strictly specific, 

 the yeasts that have been adapted to this substance becoming even 

 more susceptible to the action of other poisons. 



Duclaux 8 has already insisted on the relations which exist between 

 antiseptics and foods. Formic aldehyde which has a very powerful 

 coagulative and therefore strongly antiseptic action on protoplasm may 

 actually serve as a food for micro-organisms. The Thyrotrix tennis, 

 studied in this connection by P^re" 3 , adapts itself to the presence of this 

 aldehyde and utilises it for its nutrition. Here is produced something 

 that recalls the case of the Protozoa that digest parasitic organisms. 



It is now a current idea in microbiology that Bacteria and 

 Yeasts which primarily do not make use of certain substances, adapt 

 themselves to use them as nutrient substances. Dienert 4 has published 

 a detailed work on the adaptation of the yeasts to milk-sugar. This 



1 Monit. sclent, du D r Quesnecille, 1890, 1891, 1892, 1894. 

 3 "Traite de Microbiologie," Paris, 1898, t. I, p. 238. 



3 Ann. de TInst. Pasteur, Paris, 1896, t. x, p. 417. 



4 Ann. de TInst. Pasteur, Paris, 1900, t. xiv, p. 139. 



