This knowledge was more recently applied by the distinguished Frenchman whom I have already mentioned, M. Pasteur, in the case of a fatal pestilence among sheep in many parts of France, known by the name of _charbon_. The inoculated sheep died, however, in such large numbers, though in a somewhat smaller proportion than those who had been directly infected, that he found it necessary to weaken the matter which he employed by admixture with other innocuous materials. This experiment, however, again yielded unsatisfactory results; slight symptoms of the disease were produced, but the protection thus afforded was inadequate and uncertain. Some few resisted the disease, but others contracted it and died. With that clear insight which constitutes genius, M. Pasteur next tried the experiment of inoculating the sheep first with a weak matter which produced but slight symptoms, but at the same time enabled the animal to support a second inoculation with a stronger matter; and this second inoculation enabled them to bear, unharmed, subsequent exposure to the disease. A grateful country has given a pension, and conferred well-merited honours on the man who has preserved their flocks from pestilence, but whom the silly sentimentality of the anti-vivisectionists in England would have mulcted in a fine, and, if possible, have sent to prison. That weakening of the poisonous element which Pasteur strove to attain by art, is already provided by nature in the cow-pox. The cow-pox is nothing else than small-pox modified in character, diminished in severity by passing through the system of the animal; but giving, when introduced into the system, a safeguard against natural small-pox at least as complete as that furnished by the inoculated disease.