562 POPULAR SCIENCE MONTHLY. 



become in the culture-tubes of the experimenter as harmless as those 

 found in an ordinary infusion of hay, such as the bacillus suhtilis. 

 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 Eobertson, of Leith. He re- 

 ports 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 

 himian 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 cen- 

 turies. 



The late epidemic of smallpox in the United States was the legiti- 

 mate 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 Eico, 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 in- 

 stance 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 pro- 

 tection by previous vaccination, but for the most part constituted either 

 of the vaccinated or of the children of the vaccinated. 



