SPECIAL MEDIA. 107 



nipulation. It is better not to add the litmus tincture 

 before sterilizing the tubes, as its color-characteristics 

 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. 



Losffler's blood-serum mixture. Loeffler'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. It requires for its solidiiication 

 a somewhat higher temperature and a longer exposure 

 to this temperature than does blood-serum to which no 

 bouillon has been added. (See also the Councilman- 

 Mallory method.) 



Guarniari's agar-gelatin : 



Meat-infusion . 950 c.c. 



Sodium chloride 5 grammes. 



Peptone .... . . . 25-30 " 



Gelatin 40-60 " 



Agar-agar . . 3-4 " 



Water . . 60 c.c. 



The point in the jjreparation of this medium is its 

 reaction, which should be exactly neutral. 



The full list of special media is too great to be given 

 in a work of this size. For their description the reader 

 is referred to the current literature on the subject. 

 Those that have 'been given above will suffice for ob- 

 taining a clear understanding of the principles of the 

 work. 



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

 watery extract of meat made by mixing 500 grammes 



