216 THE ORGANISMS IN YEAST. 



the air some germs of moulds or of ferments had entered, and in 

 the majority of cases it was found that the organisms developed in 

 each flask were limited to one particular species, the amount of air 

 admitted not seeming sufficient to carry with it any great number 

 or variety of organisms. Where this was the case, an uncontami- 

 nated growth of mould or ferment was obtained, and formed the 

 material for a series of successive cultivations in supplies of germ- 

 free, nutrient liquids, conducted with proper precautions to 

 secure freedom from accidental errors. The results showed that, 

 although the moulds and mildews were capable, under some cir- 

 cumstances, of acting in a degree as alcoholic ferments, yet each 

 species retained its individual character, instead of exhibiting that 

 polymorphism which had previously been claimed for the group. 

 It was also found that, in each instance, the nature of the fermen- 

 tation was in accord with the description of the cell-life present, 

 and in some instances, further, that the various nutrient liquids 

 were by no means equally capable of supporting the life of all the 

 species of organisms concerned in such changes. From this it 

 became clear that the injurious changes in materials and produce, 

 from which various industries often suffer, might reasonably be 

 ascribed to the action of these organisms whose universal preva- 

 lence would go far to account for the mystery hitherto attaching to 

 such changes. Further investigation showed that such actually 

 was the case, and that the acetic, the lactic, the putrefactive, and 

 other similar fermentations were, like the alcoholic fermentation, 

 due to the development in the affected medium of certain special 

 varieties of organism, each variety producing its particular effects. 

 In the meantime, these conclusions and theories received great 

 support from the results obtained by those scientists who had been 

 endeavouring to apply them to the elucidation of the history of 

 certain diseases, and the valuable knowledge obtained in this field 

 of research by Pasteur, Koch, and others on the Continent and in 

 this country, have, while rendering great service to humanity, con- 

 firmed in a remarkable degree the reasonings of Pasteur with regard 

 to industrial ferments. The same branches of study have further- 

 more been pursued from another and independent standpoint by 

 some of the leading Continental botanists, who, however, whilst 

 agreeing as to the effect and action of these organisms, differ con- 



