"The very virulent inoculation practiced at Pouilly-le-Fort, in order to prove the immunity produced by vaccination, had been effected by the aid of anthracoid germs deposited in a culture which had been preserved in my laboratory more than four years, that is to say, from the 21st March, 1877. There was assuredly no doubt about its virulence, since in fifty hours it killed twenty-five sheep out of twenty-five. Nevertheless, a commission of doctors, surgeons, and veterinary-surgeons, of Chartres, prejudiced with the idea that virus obtained from infectious blood must have a virulence capable of defying the action of what I call cultures of virus, instituted a comparison of the effects upon vaccinated sheep and upon unvaccinated sheep of inoculation with the blood of an animal which had died of splenic fever. The result was identical with that obtained at Pouilly-le-Fort--absolute resistance of the vaccinated and deaths of the unvaccinated. If I were not pressed for time I should bring to your notice other kinds of virus attenuated by similar means. These experiments will be communicated by-and-by to the public." The bearing of these researches of Pasteur on vaccination with cow-pox, and the whole of the Jennerian doctrines, will be evident. They throw a flood of light both on the efficacy of vaccination and the many supposed failures which have given a handle to the unscrupulous fanatical detractors of Jenner and his doctrines. They go far toward establishing the correctness of the view entertained by Jenner as to the identity of small-pox and cow-pox, showing how great may be the modifications effected in the original virus by repeated transmission, either through the animal or the human system.