488 LEWIS DAVIS 



small "starter" flasks. Incubation is for at least ten days at 

 36°-38°C, with a twelve-day period preferred. Data are pre- 

 sented showing that the H ion concentration of the medium 

 during growth cannot be used as an index of diphtheria toxin 

 production. 



7. Results are tabulated which have been obtained during the 

 past year in the production of several thousand gallons of diph- 

 theria toxin according to the procedure discussed. Practically 

 90 per cent of this toxin was of serviceable strength, — L + dose 

 = 0.50 cc. or less. Of this more than 78 per cent was high 

 strength, having an L+ dose of 0.33 cc. (M. F. D. = 0.0033 cc.) 

 or less, and 43 per cent had an L+ dose of 0.25 cc. (M. F. D. = 

 0.0025 cc.) or less. 



The efficiency of this toxin in the routine immunization of 

 horses for antitoxin is shown by records of antidiphtheric serum 

 production during the past year. Nearly 78 per cent of all new 

 horses on this treatment produced serviceable antidiphtheric 

 serum, i.e., having a potency on the first large scale bleeding 

 of 200 antitoxin units or greater. Of the productive horses, 80 

 per cent gave serum ranging from 200-1000 units, 44 per cent 

 yielded a product from 500-1000 units, and 20 per cent had serum 

 coming within the very high range from 1000 to above 1600 

 antitoxic units per cubic centimeter. 



REFERENCES 



Bunker 1919 J. Bact., 4, 379. 



Clark and Lots 1917 J. Bact., 2, 1, 109, 191. 



Cole and Onslow 1916 Lancet, 2, 9. 



Davis 1917 J. Lab. and Clin. Med., 3, 75. 



Davis 1918 J. Lab. and Clin. Med., 3, 358. 



Hurwitz, Meyer and Ostenberg 1916 Bull. Johns Hopkins Hospital, 27, 17. 



Larson, Cantwell and Hartzell 1919 J. Infect. Dis., 25, 41. 



Lotenatj 1908 Arch. f. Hyg., 66, 305. 



Madsen 1897 Ztschr. f. Hyg. u. Infskr., 26, 157. 



Martin 1898 Ann. de l'lnstit. Pasteur, 12, 26. 



MacConkey 1912 J. Hyg., 12, 507. 



Park and Williams 1896 J. Exp. Med., 1, 164. 



Roux and Yersin 1888, 1889, 1890, 1894 Ann. de l'lnstit. Pasteur. 



Smith 1899 J. Exp. Med., 4, 373. 



Spronck and von Fourenhotjt 1895 Ann. de l'lnstit. Pasteur, 9, 758. 



Spronck 1898 Ann. de l'lnstit. Pasteur, 12, 700. 



