INOCULATION OF GELATINE AGUE. 



55 



To hasten the procedure and lessen the danger of contamina- 

 tion, the tubes can be held in one hand aside of each other, each 



FIG. 25. 



FIG. 26. 



Manner of holding plugs. 



plug opposite its tube. They are now read}' for spreading on 

 glass plates. 



Glass Plates. The larger the surface over which the nutrient 

 medium is spread the more isolated will 

 the colonies be ; window glass cut jn rec- 

 tangular plates 0x4 inches in size is used ; 

 about ten such plates are cleaned with dry 

 towel and placed in a small iron box or 

 wrapped in paper ; and sterilized in the 

 hot-air oven at a temperature of 150 C. 

 for ten minutes. (Fig. 20.) When the 

 plates have cooled they are placed upon 

 an apparatus designed to cool and so- 

 lidify the liquid media, which is now 

 poured upon the plates from the inocu- 

 lated test-tubes. 



A 



Iron box for glass plates. 



Nivellier Leveling and Cooling Apparatus. Ice and water 

 are placed in a shallow round glass tray ; on top of this a square 

 plate of glass, upon which the culture plate is placed, and cov- 

 ering this a bell-glass. 



The whole is upon a low, wooden tripod, the feet of which 

 can be raised or lowered, and a little spirit-level used to adjust 

 it. (Fig. 27.) The glass plate taken out of the iron box is placed 

 under the bell-glass. The tube containing the gelatine is held 



