Louis Pasteur

“ The microbe, in developing itself, will speedily take all the oxygen of the tube and of the liquid, after which it will be quite free from contact with oxygen. In this case, it does not appear that the microbe becomes appreciably attenuated, even after a great lapse of time. The oxygen of the air, then, would seem to be a possible modifying agent of the virulence of the microbe of chicken-cholera—that is to say, it may modify more or less the facility of its development in the body of animals. May we not be here in presence of a general law applicable to all kinds of virus? ”

“ I can not conclude, gentlemen, without expressing the great pleasure I feel at the thought that it is as a member of an international medical congress, assembled in England, that I make known the most recent results of vaccination upon a disease more terrible, perhaps, for domestic animals than small-pox is for man. ”

“ It will be readily seen, from an inoculation of a series of ten fowls, that the virulence of one culture differs from that of the blood, and from that of a preceding culture, when a sufficiently long interval elapses between the impregnation of one culture with the microbe of the preceding. More than that, we may recognize, by this mode of observation, that it is possible to prepare cultures of varying degrees of virulence. One preparation will kill eight fowls out of ten, another five out of ten, another one out of ten, another none at all, although the microbe may still be cultivated. ”

“ When the fowls have been rendered sufficiently ill by the attenuated virus which the vital resistance has arrested in its development, they will, when inoculated with virulent virus, suffer no evil effects, or only effects of a passing character. In fact, they no longer die from the mortal virus, and, for a time sufficiently long, which in some cases may exceed a year, chicken-cholera can not touch them, especially under the ordinary conditions of contagion which exist in fowl-houses. ”

“ The virus from the rabbit in which the incubation has been long, is inoculated, by trepanning, into a second rabbit, and the virus from this one into a third. With each successive transfer, some of the virus, which becomes stronger and stronger each time, is inoculated into a dog, who becomes gradually more hardened against the operation of the poison, until he is finally found capable of withstanding a fatal virus. He then becomes entirely insusceptible to rabies, the virus of a mad dog producing no effect upon him, whether introduced by intra-venous inoculation or by trepanning. ”

“ One cell makes two or more, which form themselves in wreaths; the cells become detached, and the process recommences. In these cells real germs are not usually seen. The microbe of chicken cholera and many others behave in this way, so much so that the cultures of this microbe, although they may last for months without losing their power of fresh cultivation, perish finally like beer-yeast which has exhausted all its aliments. The anthracoid microbe in artificial cultures behaves very differently. ”

“ The forty dogs should be caused to be bitten successively by rabid dogs. If the statements which I have made are correct, the twenty dogs deemed by me insusceptible will all escape, while the other twenty will be attacked by rabies. In a second experiment, not less decisive, forty dogs would be used, of which twenty had been previously vaccinated, and the others had not. The forty dogs should be trepanned with the virus of a mad dog. ”

“ The good-will of your esteemed president has decided otherwise. How could one, in fact, resist the sympathetic words of that eminent man, whose goodness of heart is associated in no small degree with great oratorical ability? ”

“ Among the inferior organisms, all do not resolve themselves into those corpuscle-germs which I was the first to point out as one of the forms of their possible development. Many infectious microbes do not resolve themselves, in their cultures, into corpuscle germs. ”

“ You deal in the same way with a third culture-vase, with a fourth, and so on to a hundred, or even a thousand, and invariably, within a few hours, the culture-liquid becomes turbid and filled with the same minute organisms. ”

“ In a short time, if the little culture-vase is placed in a temperature of 25° to 35°, you will see the liquid become turbid, and full of tiny microbes, shaped like the figure 8, but often so small that, under a high magnifying power, they appear like points. ”

“ The preliminary experiments are very favorable to this opinion, but the tests must be infinitely multiplied on various species of animals before therapeutics will have the boldness to try this preventive on man. ”