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Scientific Proceedings (132) 



these bottom precipitates, as they will be found to be present in 

 the controls as well. 



It may be of interest in this connection to give the titration 

 results of an extract antigen prepared as outlined in a previous 

 paper of these Proceedings, 1 and the same extract containing 400 

 and 800 mgm. of cholesterin per 100 c.c, respectively. 



This titration would indicate that cholesterin plays an impor- 

 tant role in necessitating proportionally larger amounts of salt 

 solution to bring about opalescent antigen-salt solution mixtures. 

 It might be added also that in a general way, cholesterin propor- 

 tionally increases the sensitiveness of the antigen after mixing 

 with syphilitic serum. The problems involved in the cholester- 

 inization of antigen are reserved for further studies. 



241 (2201) 



Employment of different antigens in Kahn precipitation test. 

 By R. L. KAHN and W. \V. DUEMLING. 



[From Bureau of Laboratories, Michigan Department of Health, 



Lansing, Mich.] 



Employing the antigen titration outlined in the previous paper, 

 the question arose to what extent the preparation of antigen 

 may be varied without affecting the final results. The following 

 antigens were accordingly prepared, titrated with salt solution 

 and smallest amounts of the latter used which produced opales- 

 cent antigen-salt solution mixtures. The tests were carried out 

 with positive and negative sera according to procedures I and II. 



Antigen 1. This was prepared as described in a previous paper 

 of these Proceedings. 1 Dried beef heart was freed from ether 

 extractives and subsequently extracted in 95 per cent, alcohol 

 for 9 days in the ice box and overnight at incubator temperature. 

 Color approximated potassium bichromate color standard. 



Antigen 2. After extracting the dried heart with ether in the 

 usual manner, boiling alcohol was poured on the dried material, 

 shaken and extraction continued for 1 day in the incubator. 

 Color approximated potassium bichromate standard. 



i Kahn, R. L., Proc. Soc. Exp. Biol, and Med., 1923, xx, 325. 



