It occurred to Dr. Jenner that if this inoculation with cowpox would protect these milkmaids, it would be an infinitely safer thing to use to protect children than even the mildest known form of inoculation. So he tried it upon two or three of his child patients, after explaining the situation to their parents, and was perfectly delighted when, a few months afterward, these children happened to be exposed to a severe case of smallpox and entirely escaped catching the disease. This was the beginning of what we now call _vaccination_. The germ of cowpox, which is believed to be either the cow or horse variety of human smallpox, is cultivated upon healthy calves. The matter formed upon their skin is collected with the greatest care; and this is rubbed, or scraped, into the arm of the child. It is a perfectly safe and harmless cure; and although it has been done millions of times, never has there been more than one death from it in 10,000 cases. In a little over a hundred years it has reduced smallpox from the commonest and most fatal of all diseases to one of the rarest. But in every country in the world into which vaccination has not been introduced, smallpox rages as commonly and as fatally as ever. For instance, between 1893 and 1898 in Russia, where a large share of the people are unvaccinated, 275,000 deaths occurred from smallpox; in Spain, where the same condition exists, 24,000. In Germany, on the other hand, where vaccination is practically universal, there were in the same period only 287 deaths--1/1000 as many as in Russia; and in England, only a slightly greater number. Another illustration, which comes closer home, is that of the Philippine Islands. Before they were annexed by the United States, vaccination was rare, and thousands of deaths from smallpox occurred every year. In 1897, after the people had been thoroughly vaccinated, there was not a single death from this cause in the whole of the Islands. [Illustration: BILL OF HEALTH No outgoing ship may "clear the port" without a Bill of Health, signed by the Collector of Customs and the naval officer of the Port.] This discovery of Jenner's was most fortunate; for vaccination remains until this day absolutely the only remedy of any value whatever that we possess against smallpox.