Page:Popular Science Monthly Volume 59.djvu/572

562 become in the culture-tubes of the experimenter as harmless as those found in an ordinary infusion of hay, such as the bacillus subtilis. Even thus the wild boar is proven the ancestor of the domestic hog, and the wild-cat the remote progenitor of the Angora kitten.

Even scarlet fever, under the impulse of some such causes as those under discussion, has evolved a 'new type,' which has been set forth by a competent health officer. Dr. William Robertson, of Leith. He reports that compulsory notification has not only lowered the mortality of scarlet fever, but actually modified its type, so much so that it is now difficult to tell when one has or has not to deal with the suspected disorder. On every side one hears it repeated that epidemics are now characterized by a want of symptoms and signs. The bright red rash is seldom seen, and when there is a rash it disappears before the arrival of the medical attendant. If one looks for throat-signs, they, too, may have been transitory. The symptoms of onset are so slight that even an anxious parent takes no notice of a passing indisposition.

These are the evidences, oftentimes somewhat vague, but again both significant and unmistakable, that the dream of the scientist is to have its realization in the future. Few believe that the great pests of the human family will be suddenly jugulated or annihilated. The gradual extinction of each by modification, by attenuation of virus, and by elimination of grave symptoms, is the aim of scientific medicine, and its disciples can thank God and take courage for the fruits of their labor, realized each year in larger measure and with fuller promise.

The germ of all epidemics of smallpox is one, but the soils on which it has grown are many. The culture-tubes and culture-plates on which it has been propagated until it has lost much of its potency and even many of its features are the bodies of the men and women of the last quarter of the nineteenth and the early part of the twentieth centuries.

The late epidemic of smallpox in the United States was the legitimate fruit of the Spanish-American War, and the popular terms by which it was designated among the common people, like almost all folk-words, contained a kernel of truth. Cuba and Porto Rico, before our armies descended upon their shores, were like the Philippine Islands, very abiding-places and citadels of smallpox. Our returning troops brought back with them the effective elements which lighted up the late epidemic in the United States. But the germ-carriers in this instance were our own previously vaccinated soldiers. The germ was attenuated in its potency at the outset. When it gathered to itself the added power by which it was enabled to spread from community to community, its extension was not through a population virgin of protection by previous vaccination, but for the most part constituted either of the vaccinated or of the children of the vaccinated.