162 LABORATORY METHODS OF 



Agar and gelatine are simply bouillon hardened, or 

 stiffened by them. 



Everything must be labelled in the laboratory ac- 

 cording to the model shown you. 



Examine an inoculating needle, draw and learn the 

 use of the same in more than one method. 



Notice the demonstrator, as he inoculates one tube. 

 Describe in full the process in your notebook. 



Inoculate several agar and gelatin tubes, some on a 

 slant surface and some on a square surface. 



It is necessary that the glassware be thoroughly 

 cleaned before it is used. Several methods have been 

 suggested, but the best is the one which follows: 

 First, take cleaning fluid and wash the vessels in if. 

 The fluid is made as follows : dissolve 80 grams of 

 potassium bichromate in 300 c.c. of warm water; 

 when cooled, slowly mix the solution by constant stir- 

 ring with 450 grams of sulphuric acid ; store the liquid 

 in a glass bottle with glass stopper. 



CLEANING TEST-TUBES. 



Wash them in warm soapsuds; then place them in 

 the cleaning fluid, twenty minutes; then pour the solu- 

 tion back into the bottle ; wipe the tubes dry and drain 



