482 ARMAND RUFFER. 
animal recovered from an infectious disease that animal was 
unable to contract it again. It was said to be vaccinated 
against that particular kind of micro-organisms. Actual ex- 
periment soon showed that it was possible to artificially 
vaccinate an animal against some fungi by the inoculation of 
an attenuated form of the same germs (Pasteur, Chauveau), or 
even by the injection of the poisons secreted by the same’ 
micro-organisms in artificial cultures (Charrin, Salmon and 
Smith, Roux and Chamberland, Chantemesse and Widal). 
The bacillus of anthrax, for instance, having no or very little 
harmful influence on a dog, on a vaccinated sheep, rabbit, or 
guinea-pig, was always mortal to the three latter species of 
animals if they were not previously subjected to a preventive 
inoculation of the attenuated anthrax bacilli. The Bacillus 
pyocyaneus injected into the rabbit’s veins proved fatal to 
that animal in a period varying from twenty-four to forty- 
eight hours, but produced a temporary illness only when 
introduced into a rabbit vaccinated with 15 or 20 c.c. of the 
sterilised culture of the same bacillus. 
Now, Metschnikoff! and Hess* have proved that the blood or 
lymph of the dog, of the vaccinated rabbit or guinea-pig, were 
most excellent media for the cultivation of the anthrax bacillus; 
in other words, the blood of these animals did not contain any 
chemical compounds capable of arresting the growth of that 
micro-organism. Another hypothesis assuming that micro- 
organisms secreted a vaccinating substance which, when intro- 
duced into the animal, remained stored up in its cells, thus 
protecting the latter against the attacks of the former, has 
been proved to be erroneous by the experiments of Professor 
Bouchard,’ of Dr. Charrin, and myself. These experiments 
showed that the vaccinating substances secreted by the Bacil- 
lus pyocyaneus in the rabbit’s organism were excreted by 
1 Metschnikoff, ‘ Virchow’s Archiv,’ cxiv, Heft 3; ‘Ann. de |’Institut 
Pasteur,’ 1887. 
2 ¢Virchow’s Arch.,’ Bd. cix. 
* Bouchard, ‘ Compt. Rend. de l’Acad. des Sciences,’ 4th June, 1888. 
4 Charrin and Armand Ruffer, ibid., 15th October, 1888. 
