diseases so that he can dwell there permanently, he must apparently face the fact that his vitality and, still more, that of his children, will inevitably be depressed. He will not be able to work as he did in more northern climates, and he cannot have the self-control and mental activity which he there possessed. He goes to the tropics with an inheritance vastly better than that of the aborigines, and this will stand him in good stead for many generations, but yet in the end his lot seems no better than theirs, for if he stays there permanently, he is in serious danger of slipping slowly backward, simply because he cannot make the strenuous exertions by which people in more favored regions are continually going on to some new achievement.

This discouraging view is by no means justified. It is like that of the poor laborers who went about in mobs to break up machinery when the steam engine was first introduced. They thought that machinery was taking the bread from their mouths. They little realized that it would put into the hands of their children hundreds of things which in their own day were possible only for the rich. The view of South America here presented is in reality exemely hopeful. Everyone recognizes that tropical regions are backward, and that, in spite of all our optimistic talk, we have made almost no progress toward any permanent occupation or development of millions of square miles of what are probably the most productive regions in the world. We must frankly face the fact that even the little progress which has been made in recent decades is almost entirely the work of men from the north, and that generally the important things are done by the first generation, or else by people of later generations whose lives have in good measure been spent in more favored regions away from their tropical homes. Four centuries ago the world stood face to face with the wonderful opportunity of a new world. For a hundred years almost nothing was done in the way of permanent colonization. Except for a few Spanish colonies Europe was content merely to explore and exploit. Then the temperate regions of North America began to be settled, and to grow great, and later their example was followed

by the temperate lands of South America. Today our attitude toward the less favored tropical portions of South and Central America is almost like that of Europe toward America as a whole three hundred years ago. In 1600 A. D. not a single successful colony had been established in what are now the most successful parts of the New World. That fact might then have seemed as discouraging as does our present lack of success within the tropics.

The comparison that has just been made does not quite cover the real conditions. We might better compare ourselves with a primeval group of naked, fireless, houseless savages who want to inhabit a land where the winters are long and cold. Such men would say that while an occasional man, hardier than his fellows, might stay in such a land through the winter, and while it might be possible for many people to go there in summer, permanent occupation of the country was absolutely out of the question. This view would not be at all unreasonable. Yet if some happy accident led one of the savages to discover how warm a man might be when he stripped the hide from a bear and threw it around himself, how quickly there would be a change of opinion. When fire became known opinion wou. change still more. And when some lucky genius discovered that a man could pile up stones or sticks and cover them with mud or skins or grass and thereby form a house which would keep out rain, snow and wind, and within which a fire could be made, would not the whole tribe laugh at their former lack of faith? Or rather would not each one say that he had always expected some such thing, and that he was on the very point of making a bearskin coat, inventing a house and discovering fire when someone else got ahead of him?

Today we are like these savages. We have long recognized that there is some fatal influence which has kept tropical regions from developing on a par with temperate regions. The vast majority of us believe that this is due to climate. Our trouble has been that we have not understood exactly how climatic influences work. We have not known whether they actually cause the human mind to deteriorate, or

whether they merely hinder its development. We have not known whether the white man can live and thrive in the tropics, or whether he must inevitably deteriorate. Only one thing has been clear, namely, that the most obvious tropical hindrance is the terrible prevalence of disease. This we have attacked, and our final success can scarcely be doubted, although there is a vast amount still to be done. We have reached the position of the savages after they discovered the use of clothing, but before they had learned to use fire and houses. Our next task is to find out more precisely how temperature and changes of temperature, together with humidity and other climatic factors, affect the human system. We must measure all sorts of physiological and psychological functions in terms of these factors, and we must be able to work out the exact measure of the influence of any given type of climate. Then we shall be ready to search for remedies. Perhaps we shall devise some means of varying our supply of oxygen. Possibly we shall give the people of tropical regions the necessary variety of climate by moving them in wholesale fashion from the mountains to the plains and back again at short intervals. Possibly we shall devise a plan whereby some means of creating the stimulus which now comes from the optimum temperature and from frequent changes shall be as much a part of a tropical house as a stove or furnace is a part of a house in regions with cold winters. All these are vague suggestions, but they indicate the sort of things that may perhaps be done. The future of South America depends largely on our success along these lines. We have conquered low temperature in large measure. Our next great task is to conquer the uniform heat of the lands within the tropics.