THE MICROBIAL TOXINS. 73 



theria, and due to the toxin passing through the 

 mucosa. In spite of this property, however, the 

 diphtheritic poison may be taken into the stomach 

 without any pernicious results. 



Roux and Yersin have shown that, like all the 

 diastases, it may be precipitated from its solutions 

 by the development, within these, of certain pre- 

 cipitates, particularly calcium phosphate. It is 

 precipitated from its solutions by alcohol, as has 

 been observed also in the case of diastatic solutions. 

 All the toxic substance is contained in the albu- 

 minous precipitate thus obtained ; but the prolonged 

 action of alcohol, or repeated successive precipita- 

 tions, alter it finally. Diphtheria toxin is likewise 

 precipitated by the reagents for albumoses, par- 

 ticularly sodium sulphate in saturated solution. 

 This procedure has been utilized by Brieger and 

 Fraenkel for preparing the pure toxin, which 

 they obtained in the form of very light, brilliant 

 white, amorphous flocks, affording all the principal 

 reactions of the soluble albumoses (biuret, xantho- 

 proteic, Millon's), and which they characterized 

 as a toxalbumin. 



On injecting into healthy animals this diphtheria 

 toxin attenuated by sufficiently heating at 70 C., 

 employing at first small doses, and gradually 

 increasing, it is possible to immunize them against 

 diphtheria, as was first demonstrated by Carl 

 Fraenkel. 



