214 



BACTERIOLOGY. 



to give it the desired reaction, which is for most bac- 

 teria slightly alkaline to litmus. If the fluid is clear 

 it is put into flasks and tubes and sterilized; if not 

 clear, the white of one or two eggs is added to the 

 fluid after cooling it down to about 55 C. After 



FIG. 21. 



Autoclave for sterilization with live steam under pressure. 



thoroughly mixing the eggs the bouillon is boiled 

 briskly for a few minutes and then again filtered and 

 distributed in flasks and tubes and put in the Arnold 

 sterilizer for one hour on each of two consecutive days, 

 or in the autoclave for twenty minutes for sterilization. 

 Instead of meat 2 to 4 grammes of Liebig's or some 

 other meat extract are added to each litre of water. 

 For most purposes the extract is as good as the fresh 

 meat, but for toxin production it is inferior. 



