cause. If liquor drinking is correlated with greater physical vigor in men, an elimination of drinkers is also an elimination of vigor, and would result in race deterioration. Social causes are simpler and deeper seated than are social effects. A study of the types of men and of the relation between the various groups of visible traits must therefore precede attempts to modify races by the elimination of single traits.
Prominent differences in men arise from the contrasting effects of upland and lowland climates. An upland race, if in a dry region, has a purer and more bracing atmosphere, and hence does not need so much lung power. It must develop greater vigor and endurance, partly because of the cold and partly because of the game it chases and the cattle it herds. Its food is drier, harder and more condensed; hence a better development of the jaw and its muscles results; along with this come smaller stomachs, better digestion and fresher blood. A tall, narrow-chested man comes into being, who is in marked contrast with the short broad man of the lowland regions. These typical differences are accompanied by minor traits, not always found in all of a given race, but often enough to indicate that they have the same general causes. Long heads and round heads represent dynamic changes, even if we can not trace them back to given climatic origins. Some races and persons have a marked development of the lower face with prominent jaws and strong facial muscles. These people like hard foods, enjoy chewing their food, and, if possible, keep something in their mouth, gum or tobacco or the like, to exercise their jaws. Baseball players are noted examples of this habit; it indicates a surplus of energy and strong muscular development. It is equally plain that those with a weak lower jaw and muscles take readily to soft sweet foods, that they suck or gulp down rather than chew. This means a better muscular development of the throat. A snake, for example, sucks down its food, while a tiger chews his. In men the sweets and the meats are causes that bring out this difference between the chewers and suckers. Another like contrast is between the mouth breathers and the nose breathers. We speak of breathing as a habit, and yet different habits would not tend to be formed if muscular differences did not exist. Each activity is the outlet of energy, which tends to express itself through bodily mechanisms. The strong grows at the expense of the weak; each difference in bodily powers tends to develop a type.
These contrasted traits are valuable, not so much for the definiteness of their manifestation as for the general conclusion their study warrants. The two types of men differ somewhat in their dynamic characters, but more in the environmental modifications which climate, food and occupation have created. The upland types are tall, bony, narrow-chested with well developed lower faces. They breathe through the nose and eat hard foods. The lowland types are short, thick set, live on soft foods, and use large quantities of coarse or liquid foods.