54 



MICROBES AND TOXINS 



mycelium into a yeast-like form, which also produces fermenta- 

 tion like a true yeast, was discovered by Pasteur, who thought 

 that in the course of ages the yeasts had been evolved 

 from moulds which had become adapted to the fermentative 

 life. 



FIG. 20. The yeast of beer: high 

 or tumbling yeast. 



FIG. 21. Spindle-shaped 

 yeast. 



FIG. 22. The yeast of 

 wine. 



FIG. 23. The yeast of beer : low 

 or heavy yeast. 



Yeasts. Yeasts are fungi of the Blastomycete group. 

 They consist of round or elliptical cells which multiply as a 

 rule by budding ; some multiply by equal division into two 

 parts. Yeasts may furnish spores, which number 2 to 10, 

 and may remain enclosed in the mother cell until by the 

 bursting of this latter their germination becomes possible. 



