TECHNIQUE OF MAKING PLATES. 131 



platinum wire (Fig. 23, a) about 5 cm. long, twisted 

 into a small loop at one end and fused into a bit 

 of glass rod, which serves as a handle, at the other 

 extremity. This loop is one of the most useful of bac- 

 teriological instruments, as there is hardly a manipula- 

 tion into which it does not enter. Under no circum- 

 stances is it to be employed without having been 

 passed through a gas-flame until quite hot, for the 

 purpose of sterilization. One should form a habit 



Fig. 23. 



h 



Looped and straight platinum wires in glass handles. 



of never taking up one of these platinum-wire needles, 

 as they are called, for they are curved and straight (Fig. 

 23, b) as well as looped, without passing it through 

 a flame ; and the sooner the beginner learns to do this 

 as a reflex action, the sooner does he eliminate one 

 of the possible sources of error in his work. It must 

 be remembered, though, that it should not be used when 

 hot, otherwise the organisms taken upon it will be killed 

 by the high temperature ; after sterilization in the flame 

 one waits for a few seconds until it is cool before using. 

 A minute portion of the material under consideration 

 is transferred with the sterilized loop into tube No. 1, 

 " the original," where it is thoroughly disintegrated by 

 gently rubbing it against the sides of the tube. The 

 more carefully this is done the more uniform will be 



