THE BACTERIOLOGICAL LABORATORY 37 



in the lid (i.e. between the two walls) is heated by 

 means of the prolongation (see Fig. 12). It will be 

 seen that the whole apparatus is essentially a hot- 

 water jacket. The temperature of the steriliser 

 should be maintained for an hour at 60 C. on five 

 or six successive days. By this means the fluid 

 serum is completely sterilised, but it is not solidi- 

 fied. To solidify the serum the piece of apparatus 

 represented in Fig. 13 is required. It is a double- 

 walled case, also made of stout tin (13J in. longx 

 13 J in. widex4j in. deep). It is provided with a 

 copper bottom, glass cover, water-gauge, and ther- 

 mometers ; there is also an arrangement by which 

 this inspissator, as it is called, can be fixed at the 

 angle required; this being necessary to give the 

 serum a sloping surface. The tubes, etc., containing 

 the sterile but fluid serum, are placed in the inspis- 

 sator ; and this apparatus (like the serum steriliser) 

 containing water (between the two walls) is heated 

 from below. To coagulate the serum, and to solidify 

 nutrient agar-agar, a temperature between 65 and 

 68 C. should be maintained ; but as soon as solidi- 

 fication takes place the tubes should be removed 

 from the inspissator. Solidified blood serum is used 

 for the cultivation of Bacilhis tuberculosis, Bacillus 

 mallei, and a few other microbes ; but we shall refer, 

 in detail, to the various cultivation media and the 

 methods of cultivation, in the next chapter. 



Incubators. Many microbes are capable of being 

 cultivated at the ordinary temperature of the 

 laboratory; but certain microbes require a higher 

 temperature for their proper development and mul- 



