his humility and disinterestedness. In-writing of this period he says, "While the vaccine discovery was progressive, the joy I felt was at the prospect before me of being the instrument destined to take away from the world one of its greatest calamities."
What he really accomplished during those twenty-five years of preparation and waiting is, succinctly, as follows:
1. He perceived that some profound modification of the effects of the virus of smallpox occurred when it was introduced through a puncture in the skin, instead of finding its way to the system through the natural channels of the lungs and the stomach.
2. That cow-pox was really smallpox in cows,[1] but that the disease in passing through the tissues of that animal underwent a still greater modification, by which its period was lessened, and that it became non-contagious, unless a person brought in contact with it had some abrasion of the skin.
3. That persons who had accidentally acquired it from the cow did not give it to others while passing through it, and were henceforth secure from attacks of smallpox.
It was his putting of "this and that together" that made the great step forward: could this modified virus be inoculated successfully into the human system as smallpox had been; and, if so, would it protect against smallpox? James Phipps had furnished the triumphant answer, and his other twenty-two cases had confirmed its truth. He did not find a second opportunity for putting his hypothesis to the test till 1798; he then repeated his inoculations with the utmost care, and prepared his book for printing. Before giving his work to the press, he devoted the most solemn and conscientious care to it, reading it sentence by sentence to a few of his most intimate friends and asking for their unsparing criticism. Its title was. An Inquiry into the Causes and Effects of the Variolæ Vaccinæ (Cow-pox). These friends saw in it a great victory of the sagacity of man over one of the most fatal of diseases, and they urged him forward in his purpose of opening for the benefit of all "the stream of life and health he had been permitted to discover"; in their enthusiasm they said "he seemed to hold in his hand one of the gates of death, with power to close it." In addition to the great fact that constituted the vital kernel of his discovery, he had incidentally learned much besides. He was convinced that there were two similar-appearing diseases affecting cows that could be imparted to man, one of which he named "spurious," and which afforded no protection against smallpox. He also learned that there were rare cases where per-
- ↑ An opinion confirmed by an account of experiments published in La Semaine Médicale, December 31, 1890, made by Elternod, of Geneva; Haccius, the Director of the Vaccine Institute of Lancy; and of Dr. Fischer, Director of the Vaccine Institute at Carlsruhe in Germany
