ity which they have acquired in the course of a longer and severer elimination of the less fit than our North-European ancestors ever experienced in their civilized state. Such selection has tended to foster not so much bodily strength or energy as recuperative power, resistance to infection and tolerance of unwholesome conditions of living. For many centuries the people of south and central China, crowded together in their villages or walled cities, have used water from contaminated canals or from the drainings of the rice fields, eaten of the scavenging pig or of vegetables stimulated by the contents of the cesspool, huddled under low roofs, on dirt floors, in filthy lanes, and slept in fetid dens and stifling cubicles. Myriads succumb to the poisons generated by overcrowding and hardly a quarter of those born live to transmit their immunity to their children. The surviving fittest has been the type able to withstand foul air, stench, fatigue toxin, dampness, bad food and noxious germs. I have no doubt that if an American population of equal size lived in Amoy or Soochow as the Chinese there live, a quarter would be dead by the end of the first summer. But the toughening takes place to the detriment of bodily growth and strength. Chinese children are small for their age. At birth the infants are no stronger than ours. The weaker are more thoroughly weeded out, but even the surviving remnant are for a time weakened by the hardships that have killed the rest.
I would not identify the great vitality of the Chinese with the primitive vitality you find in Bedouins, or Sea Dyaks, or American Indians. This early endowment consists in unusual muscular strength and endurance, in normality of bodily functions, and in power to bear hardship and exposure. It does not extend to immunity from disease. Subjected to the conditions the civilized man lives under savages die off like flies. The diseases that the colonizing European communicates to nature men clears them away more swiftly than his gunpowder. Entrance upon the civilized state entails a universal exchange of disease germs and the necessary growth of immunity. Now, it is precisely in his power to withstand the poisons with which close-dwellers infect one another that the Chinaman is unique. This power does not seem to be a heritage from his nomad life of five or six thousand years ago. It is rather the painful acquisition of a later social phase. It could have grown up only in congested cities, or under an agriculture that contaminates every growing plant, converts every stream into an open sewer, and fills the land with mosquito-breeding rice fields. Such toleration of pathogenic microbes has, perhaps, never before been developed and it certainly will never be developed again. Now that man knows how to clear away from his path these invisible enemies, he will never consent to buy immunity at the old cruel price.
To the west the toughness of the Chinese physique may have a sin-