PRACTICAL APPLICATIONS OF METHOD 217 



gonococci, has been employed by many observers during recent years, 

 and promises to be of great value. 



Here, too, the production of the antigen is the only feature of 

 the reaction which has offered difficulties. Since the researches of 

 Torrey have shown that not all races of gonococcus are antigenically 

 alike, it seems necessary to produce a polyvalent antigen. At the 

 New York Department of Health at present the antigen is prepared 

 by using the ten Torrey strains. Stock cultures are carried on neu- 

 tral veal agar and, for antigen preparation, cultures are planted upon 

 a salt-free veal agar. Twenty-four-hour growths are washed off in 

 neutral distilled water, are kept in a water bath at 56 C. for two 

 hours, and are then filtered through, first, a Buchner and then a 

 Berkefeld filter. They are then sterilized for one hour. The antigen 

 so prepared is now ready to be titrated and used. 44 



44 For information concerning the details in the preparation of this anti- 

 gen we are indebted to Miss Olmstead of the N. Y. Department of Health. 



