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 Jenner’s 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. Ferran, 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 no one dared to recommend this opera- 
tion to his country in spite of the very numerous trials made in Spain. 
‘“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 on 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. 
‘Tn 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 cedema 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 cedema last, gradually dying away in 
