5o THE POPULAR SCIENCE MONTHLY the tendency is to preserve the best and strongest features and eliminate the weak and faulty ones. I remember an elaborate article in some magazine, some years ago, which explained the great prevalence of poor teeth in America by saying, that they are caused by our habit of shaving our faces, while the orientals have sore and weak eyes because they shave their heads. The filth in which the latter live was not taken into account, nor the fact that the American women, who do not shave, have as bad teeth as the men. A rather ingenious explanation of the marked disproportion between the size of the teeth and that of the jaw in many Americans, as for example, large teeth in small jaws, so that the former are crowded out of position and overlap one another, is that the big teeth are inherited from one parent and the small jaws from the other. This sounds plaus- ible and since no systematic effort has, so far as I know, been made to find out the truth of the matter, it has been tentatively accepted for want of a better explanation of an exceedingly common phenomenon. Recently some good observers, notably Dr. Sim Wallace and Dr. Harry Campbell, of England, have said that the trouble is not hered- itary at all, but begins in each person's babyhood, and that our teeth are poor and irregular and our jaws contracted because we do not exer- cise these parts sufficiently from infancy to manhood; especially from ^weaning until six years of age, when the permanent teeth begin to «rupt. In support of this statement they point out that the first set of teeth is practically never irregular, never overlaps and is very seldom defective. The beautiful lines of a baby's face are not distorted by irregular or protruding teeth, nor sunken by reason of the non-support of sufficiently wide jaws. The teeth of savages, Hottentots and Esqui- maux are almost invariably excellent, and their jaws and tongues are wider and stronger than ours. This has been proved by the measure- ment of thousands of skulls as well as by observations upon the living inhabitants of the tropics and the arctic regions. Dr. Campbell also points out that the frequent occurrence of adenoids in young children is caused by feeding them chiefly " pap." He calls this the " pap age." The good old-fashioned plan of chewing sufficiently hard and dry food to properly exercise and develop the jaws and teeth, seems to have been abandoned in our effete civilization. Instead of the honest " johnny cake " (called in the south " corn pone " or " hoe cake ") upon which such sturdy characters as Andrew Jackson and Abraham Lincoln were wont to subsist — and, by the way, the American negro had good teeth and practically escaped tuberculosis so long as he lived upon simple corn bread and bacon and the vegetables and fruits from the plantation. I started to say, however, instead of corn bread and Boston brown bread and rye and " injun " bread, the breads of our grandfathers, which required mastication and insalivation
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