172 LABORATORY METHODS OP 



from the tube to make the spread on the cover-glass. 

 This is prevented by taking the needle and heating 

 it to a bright red in the flame of the bunsen, and let- 

 ting it cool a little before placing it in the culture or 

 growth. The spreading of the material on the cover 

 and drying in the air, and then passing it three times 

 times through the flame, then applying the stain, ac- 

 cording to the special process that we will learn as we 

 go along, constitute the technic. 



METHOD OF EXAMINING THE MATERIAL THAT A PHY- 

 SICIAN MAY BRING TO YOU TO EXAMINE. 



Several cover preparations must be made; one to 

 be stained with Gram's method, another to be stained 

 with carbolfuchsin, one with gentian violet, and an- 

 other with a mordant to stain the spores, if any are 

 present. 



Gelatin plates should be made and kept at room 

 temperature. Now, if no growth has appeared on the 

 plates in twenty-four hours, it is well to try some oth- 

 er medium. But, if a growth does occur, you must 

 take a tube for your research that has only about 200 

 colonies on it. Now the first question to decide is, 

 Are all the colonies of one or of many species? The 

 question is answered by noting the characteristics of 

 the different species. This is not always known. Note 



