Page:Popular Science Monthly Volume 57.djvu/135

Rh 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 chemical constitution. The washings could, therefore, be prepared in dilute solutions of carbolic acid, and employed in the form of preserved vaccines. In 1892 and in the beginning of 1893 I made a series of experiments 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 unaltered living vaccines, as much more promising than the dead ones, especially from the point of view of the durability of the effect.