PREVENTIVE INOCULATION. 125 



inoculation was worked out, one with an attenuated virus prepared 

 from the 'virus fixe/ and another with the latter itself. The two 

 'vaccines/ when inoculated successively into Guinea pigs, protected 

 them against all possible forms of cholera infection. The vaccines 

 were cultivated on a solid medium, and when the crop of microbes was 

 ready at the end of some twenty-four hours, they were washed off the 

 surface of the medium and used as a kind of medicinal plant. It was 

 found that the substances contained in the microbes preserved to a 

 great extent their immunizing properties even when the microbes were 

 killed by some delicate processes not affecting considerably their chem- 

 ical constitution. The washings could, therefore, be prepared in dilute 

 solutions of carbolic acid, and employed in the form of preserved vac- 

 cines. In 1892 and in the beginning of 1893 I made a series of experi- 

 ments in Paris, in Netley, in London, in Cambridge, and in Calcutta, 

 with these carbolized cholera vaccines, which had been preserved in 

 sealed tubes for a period of six to seven months, and it was possible to 

 show the protective effect of the method on animals as conclusively as 

 Pasteur had done in the demonstration at Pouilly-le-Fort with anthrax. 

 For the inoculation in man, however, I decided to use at first only un- 

 altered living vaccines, as much more promising than the dead ones, 

 especially from the point of view of the durability of the effect. 

 [To be concluded.] 



