46 



PRACTICAL BACTERIOLOGY. 



do not come into direct contact with the water, but, 

 when the water boils,, with the steam. In order to 

 prevent the cooling of the steam as much as possible, 

 the sides and lid of the cylinder are covered over with 

 felt. It is best to heat the apparatus with gas-burners. 



n 



Fio. 4. — Steam Steriliser. 



but parafBu lamps may be used if the steriliser is 

 small. A convenient form is shown in Fig. 4. As 

 soon as the water thoroughly boils (that is to say, 

 when copious volumes of steam make their escape), 

 the lid' is placed on, after the wire basket, containing 

 the tubes of gelatine, has been placed in the cylinder. 



