CHAPTER XII. 

 YEASTS AND MOULDS. 



THIS chapter is devoted to a consideration of the 

 next higher groups of the plant algae above the bacteria. 

 They are the yeasts or Blastomycetes and the moulds 

 or Hyphomycetes. That there is any sharp separation 

 of these forms from the bacteria, or even from one 

 another, cannot be maintained. There are various 

 gradations in character from the typical representa- 

 tives of the groups toward the others, so that there are 

 intermediary species incapable of classification. The 

 typical members of each family have very distinct 

 criteria and about them similar forms must be classified. 



The yeasts and moulds are very widely distributed 

 in nature, but have but slight pathogenic powers. 

 The former are of importance in the making of spiritu- 

 ous liquors, bread, etc. The moulds have little use, 

 and, except for their frequent appearance as contami- 

 nations, and in a few diseases, are of little interest 

 to the pathologist or bacteriologist. 



YEASTS. 



Yeasts are spherical or ovoid bodies with a doubly 

 contoured wall and a highly granular protoplasm oft- 

 times with fat droplets in it. They measure from 



