132 ORIGIN OF THE YEASTS 



Pasteur l was one of the first to attempt to answer this question. 

 He began in 1875 a series of investigations to find out whether the 

 yeasts could be isolated from the skin of the grapes and whether 

 they were present only at one time of the year. At different times 

 in the year he placed pieces of the vine and grape leaves in tubes of 

 sterile wort. This experiment indicated that during the autumn the 

 yeasts existed on practically all parts of the plant and that they 

 were very unequally distributed on the grapes themselves. He fur- 

 ther showed that the yeasts were present only during the period of 

 maturity in the grape, and that it was not present at other times. 

 The yeasts were found to be present during the fall, to gradually 

 disappear during the winter. 



Where do these yeasts come from? In what form do they pass 

 the winter? The problem is an intricate one. Pasteur has remarked, 

 however, that the yeast is always associated with another fungus, 

 Dematium pullulans which, according to him, is present on the grape 

 vine during the whole year. Pasteur thus thought that possibly this 

 Dematium pullulans developed into the yeasts, and this theory seemed 

 more plausible when it is remembered that this fungus has yeast-like 

 stages in its life cycle. This idea of Pasteur's corroborated the 

 assertions of the botanist Brefeld for whom the yeasts were only de- 

 velopmental forms for more complex fungi as the Ustilagines. Pas- 

 teur expressed it thus: " The yeast cells originate from little brown 

 bodies (cysts of Dematium) which the microscope demonstrates so 

 abundantly among the pollen of fruits." Pasteur soon gave up this 

 idea, especially when the celebrated Chamberland showed that these 

 yeasts of Dematium did not produce alcoholic fermentation. 



This opinion has been especially maintained by Jorgensen. 2 Ac- 

 cording to this author the yeasts spring from yeast-like structures 

 of Dematium pullulans as was thought by Pasteur. These were re- 

 garded as being constantly present in the atmosphere, and on the parts 

 of grape vines, etc. These are supposed not to develope into the true 

 Saccharomyces capable of producing alcohol and forming endospores. 



Somewhat the same idea is expressed by Juhler who observed a 

 fermentation in a flask of rice starch inoculated with Aspergillus 

 oryzae which serves the Japanese in making sake. Jorgensen, also, 

 believed a relation between the conidia of this fungus and the true 

 yeast. This assertion has been sustained by Sorel. 3 



1 Pasteur. Etude sur la biere, 1876. 



2 Jorgensen, A. Der Ursprung der Hefen. Cent. Bakt. 2, 1895. Ueber 

 Ursprung der Alkoholhefen. Ber. d. Garungsphysiol. Lab. von Jorgensen. Copen- 

 hagen, 1, 1895. 



3 Sorel. Etude sur V Aspergillus oryzae. Comp. Rend. Acad. Sciences, 121, 1895. 



