YEASTS AND MOLDS 207 



Form. Round and oval cells; a thin membrane inclosing a 

 granular mass, in which usually can be seen three or four irreg- 

 ular-shaped spores. When these become full grown, they pass 

 through the cell- wall and form a daughter-cell. Sometimes long 

 chains are produced by the attached daughter-cells. 



Growth. They can be cultivated as bacteria are in bouillon, 

 but grow best in beer. 



There are several varieties of beer-yeast, each one giving a 

 characteristic taste to the beer. Brewers, by paying special 

 attention to the nutrient media, cultivate yeasts which give to 

 their beers individual flavors. 



Mixed yeast gives rise to a poor quality of beer. 



Saccharomyces Rosaceus; S. Niger; S. Albicans. These 

 yeasts are found in the air; and instead of producing alcoholic 

 fermentation, they give rise to a pigment in the culture-media. 

 They grow upon gelatin, which they do not liquefy. 



Saccharomyces Mycoderma. This yeast forms a mold-like 

 growth, or skin, on the surface of fermented liquids, but does not 

 cause any fermentation itself. It forms the common "mold" 

 on wine, preserves, and "sour-krout." 



Pathogenic Yeasts. A number of workers have interested 

 themselves in experiments with yeasts in their relation to dis- 

 ease; and under the name of blastomycetes , Sanfelice has grouped 

 yeasts that produce tumors resembling epitheliomata ; and he 

 has tried to prove that the so-called animal parasites found in 

 malignant growths, and variously known as coccidia and sporo- 

 zoa, are yeasts. These are, however, protozoa. 



Oi'dium. A form which seems to be the bridge between the 

 yeast and the molds is the oidium. Sometimes it resembles 

 the yeasts, sometimes the molds, and often both forms are 

 found in the same culture. Several are pathogenic for 

 man. 



Oi'dium Lactis. Origin. In sour milk and butter. 



Form. The branches or hyphae break up into short, rod- 

 like spores. No sporangium, as in molds. 



Growth. In milk it appears as a white mold. 



Artificially cultured on gelatin plates, or milk-gelatin plates, 



