A GRAIN OF WHEAT 45 



are minute fungi invisible to the naked eye which attack the sugar of 

 the bread and transform it into carbonic-acid gas and alcohol. The 

 course of this fermentation is controlled by the presence of lactic bac- 

 teria which prevent the growth of putrefactive organisms. But here 

 again there are lactic bacteria and lactic bacteria, yeasts and yeasts. 

 These yeasts are again populations, mixtures of different races from 

 which the microbiologist can select pure lines. Here Vilmorin's 

 method must be used, i. e., filiation from a single isolated germ. 

 Thanks to this process, Hansen and others have selected a large number 

 of strains of yeasts, each with its particular character. For science 

 of to-day beer yeast no longer exists, but in its place there are many 

 distinct and constant species just as there are many distinct and con- 

 stant species of lactic bacteria. The problem of the future will be, 

 then, to regulate bread fermentation by means of these selected 

 microorganisms. 



But certain flours do not rise well. Suitable ferments must be 

 found for them. Others, like maize flour, do not rise at all. It is 

 therefore impossible to make bread from maize alone. In 1900, at 

 the time of the World's Exposition at Paris, I was asked this question : 

 " How can we find a ferment to raise dough made from maize ? " No 

 yeast tried up to that time had been able to accomplish this. I then 

 thought of using ferment from India which I had procured through 

 Colonel Prain, director of the Kew Botanic Garden. In applying these 

 selection methods the late Mr. A. Netchich and I obtained from these 

 ferments, which are employed in Sikkim and the Khasia Mountains for 

 the alcoholic fermentation of rice and Eleusine, a leaven, which alone 

 or associated with other yeast causes maize dough to rise and thus 

 allows bread to be made from it. We dedicated this species to Dr. 

 Prain (Amylomyces Prainii = Mucor Prainii}. I take this oppor- 

 tunity of announcing this discovery and putting it in reach of all those 

 who wish to profit by it. 



