LABORATORY MAXIMS 



1. See that the working table, instruments, and all pieces 

 of apparatus used are thoroughly cleaned at the close of each 

 exercise. 



2. Unless otherwise directed, all cultures, other than those 

 in gelatin, are to be grown in the incubator. 



3. Gelatin cultures should not be put into the incubator 

 except for special purposes not described in these direc- 

 tions. 



4. In opening tubes of media or cultures always flame the 

 open end of the tube immediately after withdrawing the plug. 

 If the tubes have been standing for some time, the surface 

 of the plug should be flamed before drawing it out. Never 

 allow the tube end of the plug to touch, while out of the tube, 

 any article by which it could become contaminated. It should 

 be held by the top between the fingers. 



5. In making transfers the tubes should be held as nearly 

 in the horizontal position as possible. Cultures should not be 

 opened in currents of air. 



6. In every case where a platinum-wire loop or needle is 

 used for making cultures or withdrawing media it should be 

 carefully heated in a gas flame, or that of an alcohol lamp, 

 both immediately before and after using. The heated wire 

 must be allowed to cool before making cultures. 



7. In making plate cultures work as much as possible under 

 a hood and in still air. 



