572 PATHOGENIC MICROORGANISMS 



tion of the medium upon which they are grown. Most laboratories 

 possess one or several strains of bacilli which are empirically known 

 to be especially potent in this respect. One of the most extensively 

 used, not only in this country but in Europe as well, is the strain known 

 as "Culture Americana," or "Park- Williams Bacillus No. 8," an 

 organism isolated by Dr. Anna Williams of the New York Department 

 of Health in 1894. Throughout more than ten years of cultivation 

 this bacillus has retained its great power of toxin production. 



Because of the severity of cases of diphtheria in which the diphtheria 

 bacilli were associated with streptococci, many observers were led to 

 believe that the presence of streptococci tended to increase the toxin- 

 producing power of B. diphtheria. Experiments by Hilbert, 20 Theobald 

 Smith, 21 and others seem to have given support to this view. 



The medium most frequently employed for the production of toxin 

 is a beef-infusion broth. There are minor differences of opinion as to 

 the most favorable constitution of this medium for the production of 

 toxin. All agree, however, in recognizing the importance of pepton, 

 without which, according to Madsen, 22 no satisfactory toxin has yet 

 been produced. This is added in proportions of from 1 to 2 per cent. 

 The presence of sugars in the medium is not desirable in that it leads to 

 acid production; L. Martin 23 removes the sugars from the meat by 

 fermentation with yeast. Smith 24 accomplishes the same purpose with 

 B. coli. According to Park and Williams, 25 however, this is super- 

 fluous, the quantity of sugar present in ordinary butcher's meat not 

 being sufficient to exert unfavorable influence. 



Experience has shown that a primary alkalin reaction offers the 

 most favorable conditions for toxin production. In all cultures of B. 

 diphtherias in non-sugar free broth, there is, at first, a production of 

 acid and, while this continues, there is, as Spronk 26 has shown, little or 

 no evidence of toxin elaboration. Park and Williams, 27 in an inquiry 

 into the question of reaction, came to the conclusion that the best 

 results are obtained with a broth to which, after neutralization to 



20 Hilbert, Zeit. f . Hyg., xxix, 1898. 



21 Smith, Medical Rec., May, 1896. 



22 Madsen, Krausund Levaditi, "Haiidbuch d. Technic," etc., 1907. 



23 L. Martin, Ann. de Pinst. Pasteur, 1897. 



24 Th. Smith, Jour. Exp. Med., iv, 1899. 

 25 Parfc and Williams, Jour. Exp. Med., 1897. 

 28 Spronk, Ann. de 1 'inst. Pasteur, 1895. 



27 Parlc and Williams, Jour. Exp. Med., 1897. 



