520 PATHOGENIC MICROORGANISMS 



used by the British during the war is not described in detail because 

 we believe that for ordinary laboratory work its production is too com- 

 plicated, without offering sufficient advantages over other media. To 

 summarize, we, therefore, recommend for plating media, carrier work, 

 and isolation from spinal fluid, hormone or trypagar with a P H of 

 7.4 to 7.5, containing one-half per cent glucose, to which about 5 or 

 10 per cent of defibrinated or laked blood is added just before the 

 plates are poured. 



For the storage of stock cultures, Vedder's starch agar described 

 in the section on media has been used with satisfaction. 



Gordon 12 and others also have used coagulated egg media in slants 

 for storage of stock cultures with good results. 



Egg -yolk Medium for the Storage of Meningococcus Cultures. 13 

 The egg-yolk used may be the yolks of eggs, the whites of which have 

 been used for clearing media. One volume of the egg-yolk is mixed 

 with one-half volume of physiological salt solution. The yolk and 

 salt are thoroughly mixed, tubed and slanted. The slants are then 

 inspissated in the usual way. This can be done in an autoclave by 

 bringing the temperature up gradually without letting out the air, 

 until 14 pounds pressure has been reached, and then maintaining this 

 for twenty minutes. Great care should be taken to prevent bubbles 

 in the medium. The tubes should be plugged with paraffin, since water 

 of condensation is necessary to make the medium useful for storage. 



For fermentation reactions, solid or fluid media with various 

 sugars and litmus indicator, may be used. Gordon, whose experience 

 in this kind of work has been extensive, used for his fermentations a 

 liquid medium of simple pepton water with one per cent blood serum 

 and the sugar to be investigated, added. Elser and Huntoon 14 em- 

 ployed among other things, for their extensive fermentation work, 

 sheep serum water, ascitic broth, and broth made with nutrose. 



Resistance. The meningococcus is killed by exposure to sunlight 

 or to drying within twenty-four hours. 15 It is extremely sensitive 

 to heat and cold and by the common disinfectants is killed in high 

 dilutions and by short exposures, At C. it usually dies within two 

 or three days. 



^-Gordon, FlacTc and Hinex, Med. Kes. Com., Special Report Series, No. 3, 

 London, 1917. 



"Directions of Major Foster from Gordon's Laboratory. 



14 Elser and Huntoon, Jour. Med. Eos., 20, 1909, 371. 



15 Councilman, Mallory, and Wright, Boston, 1898; Albrecht and Ghon, loc. cit. 



