TECHNIQUE OF MAKING PLATES. . 109 



looped platinum wire, Fig. 20. This is nothing more 

 than a piece of platinum wire of about 5 em. long, 

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

 bit of glass rod, which acts as a handle, at the other 

 extremity. This loop is one of the most useful of 

 bacteriological instruments, as there is hardly a manipu- 

 lation in the work into which it does not enter. Under 

 no conditions is it to be employed without having been 



FIG. 20. 

 a 



6 

 Looped and straight platinum wires in glass handles. 



passed through the gas-flame until quite hot ; this is for 

 the purpose of sterilization. One should form a habit 

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

 as they are called, for they are both looped and curved 

 or straight (Fig. 20, 6), without passing it through the 

 flame, and the sooner the beginner learns to do this as a 

 matter of reflex, the sooner does he rid himself of 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 are killed 

 by the high temperature ; after sterilization in the flame 

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

 The bit of material under consideration is transferred 

 with the sterilized loop into tube No. 1, "the original," 

 where it is carefully disintegrated by gently rubbing it 

 against the sides of the tube. The more carefully this 



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