THERAPEUTIC IMMUNIZATION IN MAN 453 



bacilli, since in these cases there has been the greatest practical appli- 

 cation for such knowledge. 



In the case of diphtheria, though toxin will be produced on all 

 media on which the bacillus grows easily, the most favorable medium 

 for this purpose is a slightly alkaline broth made of lean beef or 

 veal infusion and containing peptone. Since acid formation hinders 

 the production of toxin, Martin 17 has suggested fermentation of the 



APPAEATUS ARRANGED FOR THE STERILE FILTRATION OF DIPHTHERIA CULTURES 



IN TOXIN PRODUCTION. 

 (After Kosenau, U. S. Hyg. Lab. Bull. 21, 1905, p. 38.) 



muscle sugar with yeast, while Theobald Smith 18 recommends pre- 

 liminary fermentation with Bacillus coll. 



Park and Williams 19 regard this as unnecessary. They recom- 

 mend a 2 per cent, peptone broth made of veal. This is neutralized 

 to litmus and 7 to 9 c. c. of normal NaOH solution to the liter are 

 added. In such a medium at 37.5 C. the production of toxin begins 

 within 24 hours and reaches its highest point in from five to ten 

 days. When at its height the process must be stopped and the cul- 

 tures exposed to a lower temperature, otherwise rapid deterioration 

 takes place because of the instability of the toxin. Even when kept 

 cold and in the dark this deterioration proceeds steadily though 

 slowly. At first, however, even under these conditions a compara- 

 tively extensive loss of toxin goes on a process sometimes spoken 

 of as "maturing of the toxin" after which the poison strikes a 



17 Martin. Ann. Past., 1896. 



18 Th. Smith. Journ. Exp. Med., IV, 1899, p. 373. 



19 Park and Williams. Journ. Exp. Med., Vol. 1, 1896. 



