96 BACTERIOLOGY. 



manipulation. It is better not to add the litmus tinc- 

 ture before sterilizing the tubes, as its color character- 

 istics are in some way altered by its contact with 

 organic matters under the influence of heat. 



"When ready it may be used as ordinary agar-agar or 

 gelatin, either for plates or slant cultures. 



Loffler's blood-serum mixture. Loffler's blood-serum 

 mixture consists of one part of neutral meat-infusion 

 bouillon containing 1 per cent, of grape-sugar, and three 

 parts of blood-serum. This mixture is placed in test- 

 tubes, sterilized, and solidified in exactly the way given 

 for blood-serum. 



Guarniari's agar-gelcdin : 



Meat-infusion 950 c.c. 



Sodium chloride . ... . . 5 grammes. 



Peptone . 25-30 " 



Gelatin ... .... . 40-60 " 



Agar-agar .... .... 3-4 " 



Water . 50 c.c. 



The point in the preparation of this medium is its 

 reaction, which should be exactly neutral. 



The list of special media is too great to be given in a 

 work of this size. Their description must be seen in 

 the original. Those that have been given above will 

 suffice for obtaining a clear understanding of the prin- 

 ciples of the work. 



Note. — The term " meat-infusion " always implies a 

 watery extract of meat made by mixing 500 grammes of 

 finely-chopped lean meat and 1 litre of water together, 

 and allowing them to stand in a cool place for twenty- 

 four hours. At the end of this time the fluid portion 

 is strained off" through a coarse towel. This represents 

 the infusion. 



