II.] PREPARATION OF CULTURE MATERIAL. 25 



It keeps solid up to a temperature of 50 C., i.e. a tempera- 

 ture higher than is ever necessary for the growth of bacteria. 

 It becomes liquid at higher temperatures, and in case of 

 necessity can be again subjected to boiling. Before con- 

 sidering it as perfectly sterile it ought to be kept like all 

 other materials for from several days to several weeks in the 

 incubator at 32 to 38 C. If quite limpid after this time it 

 may safely be considered as sterile. 



Amongst all the solid media, I have found this mixture of 

 Agar-Agar and peptone meat extract to be excellent in many 

 respects. It is beautifully limpid and solid, and an excellent 

 nourishing material. Agar-Agar alone without the admixture 

 of peptone is not satisfactory as a culture medium. 



The materials which I now prefer for the cultivation of 

 pathogenic and septic bacteria are : i. Broth (beef) and 

 peptone; 2. Solid nutritive gelatine; 3. Solid Agar-Agar 

 peptone meat extract ; 4. Fluid and solid serum of blood ; 

 all faintly alkaline. 



