YEASTS AND MOULDS. 



231 



described which is pathogenic to a number of domestic 

 animals. 1 



Yeasts and Moulds. In the course of bacteriological 

 work one constantly encounters yeasts and moulds, which, 

 although not bacteria, must nevertheless be understood and 

 recognized to avoid error. Accidental contamination of 

 tubes or plates is likely to be the result of the growth of some 



FIG. 52. 



Yeast Cells, stained with Fuchsin. (X 1000.) 



of these forms. The yeasts generally go by the name of 

 sac char omyces, of which there are several species. The 

 saccharomyccs cerevisia is the ordinary yeast of alcoholic 

 fermentation. Some of the yeasts present colored growths 

 red, white and black. They consist of large, oval cells, 

 which readily stain with the aniline dyes. They multiply by 



1 It has also been called " Necrosis bacillus," and " Streptothrix 

 cuniculi." Pearce, University of Pennsylvania Medical Bulletin, Novem- 

 ber, 1902. 



