sons had had a second attack of smallpox, and that there were cases where people who had acquired what they thought cow-pox in the natural manner had been attacked by smallpox later. He set himself to study these anomalies, and became convinced that there is one "right," strictly limited time for taking the vaccine virus, and that matter taken later will produce a pustule and severe illness, but affords no protection. Also, he learned that there is a right and a wrong way in which to insert the virus—in short, that the operation is a nice exercise of medical art. He discovered that certain eruptive diseases occurring at the same time make the best virus inoperative, and he ascertained that there are many circumstances that rapidly destroy the vitality of the virus when not properly cared for. He left the fruits of all these observations embodied in a set of rules of procedure that nearly a century of experience and medical advance has not improved upon. Of course, he could not foresee the wonderful evolution in the methods of the production of the virus that now puts, such a large and safe supply into the hands of the practitioner.
We, who tranquilly enjoy the fruits of the great deliverance from the horrible and universal plague of smallpox, see and know so little of it as not to be able to form any just conceptions of the monstrous proportions of the scourge when unchecked. The average death-rate from it throughout England was such that if applied to the present population it would give 70,000 per annum; in London alone before 1804 the annual deaths were 2,018 in a population of a million; in 1890, in a population of four millions there was just one death from smallpox. In the year 1886 there was not a death from it in Massachusetts.
Jenner went to London in April, 1798, intending to bring out his book and illustrate his doctrines on the spot. He was prepared with a pure and efficient virus that had been already tested, but to his surprise and chagrin, although he was known in the highest medical circles as a man worthy of undoubted credit and of thoroughly established scientific repute, he could not find one individual willing to submit to the operation. His pamphlet—a quarto of seventy pages—was published on June 21, 1798. Seldom has a book appeared fraught with greater consequences to mankind. When he went home he left some virus in the hands of a friend—Mr. Cline—who at the end of July inserted some of it by two punctures on the hip of a child who had hip disease, under the notion that the counter-irritation produced by it might cure the trouble. It made no difference with the original disease, but by a thorough inoculation afterward with smallpox virus the child was found proof against that disease.
When the book had had time to make its due impression, with its thoroughly wrought-out and carefully written-out series of
