23° 



MANUAL OF BACTERIOLOGY. 



The yeasts generally go by the name of saccharomyces, of which 

 there are se^Kerail species. The Saccharomyces cerevisia is the 

 ordinary yeaSt of alcoholic fermentation. Some of the yeasts 

 present colored growths — ^red, white and black. They con- 

 sist of large, oval cells, which readily stain with the aniline 

 dyes.'. They multiply by the protrusion of a little bud from 

 the cell, which develops into a new cell. In an actively germ- 



FiG. 57. — Yeast Cells Stained with Ftichsin. (X 1000.) 



inating growth of yeast these buddiag cells are readilf dis- 

 tinguished (Fig. 57). 



Yeasts have been found that were pathogenic to animals. 

 They have also been supposed to be the cause of some malig- 

 nant tumors, but this view has been, for the most part, aban- 

 doned. 



Among the moulds the varieties most commonly encount- 

 ered are the mucor, the penicillium, the aspergillus and the 

 oidium. There are various species of each of them. They 



