8 BACTERIOLOGICAL DIAGNOSIS. 
cated by the thermometer. Another method which is 
less reliable than the use of the thermometer, but which 
may be resorted to in an emergency, is to wrap the ap- 
paratus loosely in cotton-wool and to proceed with the 
heating (allowing the temperature to rise gradually) until 
the outer part of the wool is slightly singed over the 
whole of the exposed surface. 
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Fic. 6.—Steriliser. 
The special steriliser which is used in the bacterio- 
logical laboratory consists of a copper or iron oven with 
double walls and perforated metal shelves. There is a 
hole in the top, which is fitted with a perforated cork, 
through which the thermometer passes. The oven is 
mounted on a stand and heated by means of a large 
Bunsen or Fletcher’s burner. 
