YEASTS 



75 



such as a sLce of stenUzed potato or a layer of nutrient gelatin in a petri dish we will 

 iZrT^IllT :r- ^^^ ^^^ °' '"^^^ ^^ ^^^^^°P ^ strong growth of mixed 



Sow n.i?,f 7 r[' '"'^ °'°'' ^"^^''^ '=°^°"^« «°til some of them will 



show only a few, some of which may be pure cultures. 



B 



^ #' /a 



o U j^ 



Fig. 55. — Wild and pseudo yeasts. A, S. pombe. {After Lindner). B. Torulte. 

 (After Pasteur.) C, Mucor, (i) spores; (2) germinating spores and mycelium. D, 

 S. apiculatus. E, Mycoderma vini. {After Bioletti.) 



The most useful method of separation and one which is applicable to most cases 

 is that of plate cultures, first used by Koch and improved by others. In this method a 

 drop of the mixed culture is thoroughly distributed in 10 to 20 c.c. of liquefied 

 nutrient gelatin or agar. A drop of this mixture is then diluted in the same way in 

 another portion of the same medium. This process is continued until the requisite 



