304 PROTECTIVE INOCULATIONS. 



"VACCINATION BY FIXED VACCINE. 



"The method of vaccination thus worked out comprises, then, two vac- 

 cines a mild vaccine, obtained by weakening" the fixed virus ; and a 

 strengthened vaccine, which is presented by the virus itself. It is easy to 

 understand why, to obtain the weakened vaccine, we do not use an ordinary 

 virus, but a virus the nature of which has been previously fixed in the labor- 

 atory. It is because the virus, such as is found in the natural state, especially 

 when it has a saprophytic phase of development, presents such pathogenic 

 differences that there is no certainty in its application. Respecting this we 

 need only recall the story of variolization, and the great danger that an indi- 

 vidual incurred when the infectious substance from a slightly attacked sub- 

 ject was transferred to him. The mildness or the gravity of an infection does 

 not depend only on the veritable strength of the contagious substance, but 

 upon the resistance of the individual from whom it is taken. Thus it hap- 

 pened that in taking vaccine lymph from a subject lightly affected, a very 

 weak substance was sometimes produced, which was incapable of producing 

 a protective action ; and sometimes a lymph of such strength that it killed 

 less resistant individuals. The great benefit of Jenhers discovery lay in 

 that it precisely indicated a substance fixed by passages through animals, and 

 of a virulence below that which is fatal to the human organism. Another 

 example is given in the method of Toussaint of vaccination against anthrax, 

 the first of its kind, which has been obliged to make way for the method of 

 M. Pasteur, for the sole reason that the latter, based upon virus of a fixed 

 nature, presented an absolute certainty in its results which was wanting in 

 the other. Finally, in the history of cholera itself I may recall the attempt 

 made in 1885 by Dr. Ferraii, of Barcelona, who, with the object of preserv- 

 ing the population of the Peninsula from the epidemic of cholera, made 

 injections in his patients of the ordinary virus taken from dead bodies and 

 cultivated in the laboratory. The statistics of the results obtained by this 

 means showed such uncertainty that 110 one dared to recommend this opera- 

 tion to his country in spite of the very numerous trials made in Spain. 



44 The possibility of treating the animal organism by vaccines of an abso- 

 lutely fixed nature, prepared by means of special operations, constitutes, on 

 the contrary, the basis of the Pasteurian method, and here lies the whole 

 secret and the sole guarantee of the success of its application. 



"APPLICATION OF THE METHOD TO MAN. 



"The method of anticholeraic vaccination, worked out by experiments 

 on guinea-pigs, was tried upon rabbits and pigeons before it was applied to 

 man. These animals were chosen in order to have subjects very differently 

 organized, and in order to be able to generalize the conclusions, and to be 

 able to extend them to the human organism. 



" The result obtained 011 all these animals being absolutely the same, it 

 was decided to apply the operation to man. 



' ' The symptoms produced by this operation have been described in several 

 scientific magazines. The method has been tried at Paris, Cherbourg, and 

 at Moscow, on about fifty persons of both sexes, between the ages of nineteen 

 and sixty-eight, of French, Swiss, Russian, English, and American nation- 

 ality. 



' ' In every case the method has shown itself absolutely harmless to health, 

 and the symptoms that it evoked were a rise in temperature, a local sensitive- 

 ness at the place of inoculation, and the formation of a transitory oedema at 

 the same place. The first sensations are felt about two or three hours after 

 inoculation ; fever and general indisposition disappear after twenty-four to 

 thirty-six hours ; the sensitiveness and oedema last, gradually dying away in 



