Only the cold zone has any advantages in temperature, and these advantages are equally important with the fertility of the soil in accounting for the predominance of population there. Yet even where the temperature is favorable to at least physical work, there is the debilitating sameness of the tropics, the assurance that there will always be more difference between day and night than between the seasons. There, on the heights, too, the nervous drain of altitude and of lack of moisture in the air takes the place--with no advantage to the human machine--of the humidity and heat of the hot country. At every turn in Mexico climate takes toll of human energy, even if we ignore the undoubtedly debilitating effect of tropical and sub-tropical light upon the white men and upon their mixed-blood descendants as well. All these climatic factors, then, have continuous influence on the health of all the Mexican people as well as upon Mexican business. The hot, humid weather of the hot country makes those who live there low in resistance of disease, while the nervous strain of the altitudes and dryness of air in the better portions achieves a not dissimilar result in lowering resistance. It is axiomatic that the Mexicans as a people are seldom well and, as has been recorded in detail elsewhere,[3] this ill-health has been and is to-day one of the determinants of the relatively low state of progress of the country. No people who are continually sick and upon whose energies their climate is a continuous drain can work well or achieve greatly. The relation of this thoroughly recognized factor of ill-health to Mexican trade and commerce must not be overlooked. It is at the root of much of the apathy which keeps the Mexican people at their low ebb of business enterprise. It determines with peculiar insistence their predilection for the easy road, the “_mañana_ habit,” even for the dominance of outworn traditional methods in agriculture and in business. It has a great deal to do with the ease with which foreigners develop a land which has for centuries lain virtually fallow. But it places vast difficulties in the way of that development, for it keeps the labor problem continually in the foreground and vitiates much of the great advantage which the relative cheapness of that labor seems to offer. It has and will continue to have a powerful effect on trade, for it keeps even the enterprising among Mexican business men at a low standard of efficiency and makes it almost imperative that foreigners, for the present, do most of the jobbing and export and much of the retail trade and export buying of the country. This element is too likely to be lost sight of, because it is not a condition common to other lands. But it explains much that seems at first inexplicable in the difficulties of the American exporter and importer in getting the adequate representation in Mexico which he must have.