50 LABORATORY GUIDE IN BACTERIOLOGY 



These may be transferred in the same manner as colonies of 

 bacteria. Molds require very careful handling for microscopical 

 demonstration. They are best examined in water in the unstained 

 condition. 



Method of preparing molds for microscopical exami- 

 nation 



1. Transfer some of the growth to alcohol (50 per 

 cent.). 



2. When thoroughly moistened, transfer some of 

 the growth to a drop of glycerin on a slide. 



3. Spread carefully with a platinum needle. 



4. Cover with a slip and examine. 



5. If satisfactory, the preparation may be made per- 

 manent by painting a ring of asphalt around the edge 

 of the cover-slip. 



Molds may also be stained in the following manner: 



1. Place a small amount of mold on a slide. 



2. Cover with alcohol. 



3. Wash in water. 



4. Stain with gentian-violet or methylene-blue. 



5. Mount in glycerin. 

 Study of yeasts 



1. Examine a small amount of yeast taken from an 

 agar-slant in water under the high power of the micro- 

 scope. Note the manner of reproduction by " budding." 



2. Prepare a culture in liquid wort of Sacch. cere- 

 visiae. 



3. Pour the supernatant liquid of the 24-hour-old 

 culture off, and distribute the sediment on a gypsum 

 block. 



NOTE. Gypsum blocks may be prepared in the following 

 manner: Gypsum (plaster of paris) is mixed with half its vol- 

 ume of water and quickly placed in a cylinder of paper. When 



