THEORY OF WORTMANN AND DELBRttCK 101 



tact. The yeasts are able to withstand strong doses of alcohol, suf- 

 ficient to kill other organisms. They are able to live in a medium 

 which contains from 10 to 18 per cent of alcohol while other organisms 

 are killed by from 4 to 10 per cent. Generally alcohol is not assimi- 

 lated by yeasts and it is then useless to them. 



The first yeasts, which were without doubt the wild yeasts, lived 

 like other fungi in contact with air. But having taken on the ability 

 of living in decaying fruits and in the mucous secretions of trees in 

 order to secure sugar, they have competed with other organisms 

 which lived under the same conditions. In this struggle for life, 

 the yeast has been victorious against its adversaries and has sur- 

 vived, thanks to the fermenting function which constitutes a means 

 of preservation for it. Yeasts are then adapted to live after a special 

 manner away from air, secreting a large amount of alcohol which acts 

 as a toxin. 



The culture of yeasts by man has finally adapted them to anaer- 

 obic life and caused them to secrete increasingly large amounts of 

 alcohol. According to this, the primitive yeasts were aerobic and 

 slowly adapted themselves to anaerobic life. 



Experience has demonstrated that if a new wine is exposed to the 

 air, a vigorous growth of fungi takes place on the surface, consisting 

 of Botrytis, Penicillium, Dematium, bacteria, and wild and cultivated 

 yeasts. These organisms live along together for a time but as the 

 yeasts produce alcohol, the medium becomes unfavorable for some of 

 these fungi and the bacteria drop out. The wild yeasts are able to 

 withstand these quantities of alcohol for a time but they in turn are 

 killed as the concentration of alcohol increases. Finally, by means 

 of their adaptation to alcohol, the cultivated yeasts are able to be 

 triumphant over all of the various fungi which were present at first. 



The phenomenon of alcoholic fermentation permits the yeasts to 

 resist suffocation. By means of it they form alcohol and C02 and thus 

 secure the heat which is necessary for their maintenance. Wort- 

 mann and Delbriick join the theory of Pasteur but their hypothesis 

 has the merit of explaining the origin of alcoholic fermentation. 



The theory of toxin formation has raised certain objectors who 

 claim that the toxin is not generally secreted in sufficient quantity to 

 injure the organisms which make it, while the yeast produces such 

 quantities of alcohol that it is finally killed. 



Theory which Makes Fermentation a Pnase of Respiration 



Another theory, which seems to depend upon Pasteur's, is that 

 making fermentation a phase of respiration. It rests upon the fre- 



