NUTRIENT MEDIA AND METHODS OF CULTIVATION. 



119 



of neutralisation with carbonate of soda solution, the flask of broth 

 is placed in the steam steriliser for half an houi- at 100° C A 

 clear liquid results on iiltration which is transferred to plugged 

 sterihsed flasks or test-tubes, and sterilisation effected by exposing 

 them in the steam steriUser for half an hour at 100° 0. for two 



Fig. 47.~Appaeatus foe Steeilisatiox by Steam unuer pkessuhe. 



or three successive days, or by I using the apparatus for sterilising 

 b\' steam under pressure. For some bacteria a more suitable 

 cultivating medium is obtained by the adchtion of glycerine or 

 grape-sugar. 



Liquid Blood Serum. — The preparation of blood serum has 

 already been described. It may be required for cultivations before 

 the final treatmeiit -by;, which it is solidified, for example, in the 

 method of drop-cultivation, and may be used -ivith the addition of 

 glycerine or grape-sugar. Hydrocele fluid, peritoidtic and pleuritic 



