478 LEWIS DAVIS 



position, this medium did not give successful results in the hands 

 of other investigators, and found little application in practice. 

 Spronck (1898) in the same year, recommended the substitution 

 of a boiled and filtered extract of commercial yeast in place of 

 the infusion of veal or beef. However, he specifically required 

 the use of Witte peptone with his yeast product. 



Subsequent publications on media for diphtheria toxin produc- 

 tion appear to be more concerned with the reaction of the broth, 

 and also, with the kind and condition of the meat used in the 

 infusion. Veal is recommended by some in place of beef, while 

 others insist that the meat before using must be either decom- 

 posed or fermented instead of freshly killed. This is in con- 

 formity with Theobald Smith's proposal for eliminating muscle 

 sugar, which is assumed to interfere with toxin elaboration. 

 Aside from the mention that the Witte product was employed, 

 no attention appears to have been paid to peptone by later 

 investigators. 



The scarcity of Witte peptone during the past few years has 

 again directed attention to bacteriologic peptone and to the 

 methods of producing diphtheria toxin. A number of peptone 

 products have appeared, of differing composition which, while, 

 allowing growth of the more common microorganisms and of 

 Corynebact. diphtheriae, do not permit of obtaining the strong 

 toxins formerly obtained. The use of trypsinized media as sug- 

 gested by Cole and Onslow (1916) and the various modifications 

 of Martin's peptone solution which have been recommended 

 have not fulfilled practical requirements. 



In the attempt to explain the necessary conditions for the suc- 

 cessful application of some of the substitute products, rather' 

 unique views have been advanced concerning diphtheria toxin 

 formation. Bunker (1919), in a recent article suggests "thai- 

 there is a point at which toxin development is at its maximum, 

 before which and after which the potency will be lost." He also 

 states that "if time alone is made the basis of judging when toxin 

 is 'ripe,' it will be only by chance and in spite of technique that 

 any peptone will give satisfactory results." These statements 

 as will be later shown, are contrary to extended practical experi- 

 ence in the routine production of high potency diphtheria toxin. 



