Page:Popular Science Monthly Volume 80.djvu/525



HE subject of the influence of sunlight in the tropics has been the subject of extended discussion for many years, and the general opinion seems to be that the intensity of insolation is the most important factor influencing the physical welfare of the white inhabitants in those parts of the world lying within the regions which are generally considered as having a tropical climate. In considering the question of what may be regarded as a tropical climate, we are too apt to be influenced by preconceived opinions as to what the dominating factors are, and we are prone to lose sight of the fact that there is as much difference between tropical climates as between those in the temperate zones. Persons living in the tropics are almost certain, during their early years of residence, through ignorance or otherwise, radically to change their mode of living and subject themselves to hygienic conditions which they would consider inadmissible in their former homes. The races of people native to the tropical zones have no knowledge of bacteriology and pathology which would enable them to understand the measures to be taken to avoid infectious and other diseases, whereas they live in regions where the absence of a pronounced winter is favorable to the rich development of microscopical life. As a consequence, many of the ill effects which are attributed to sunlight may in reality be due to entirely different causes. Again, races native in the tropics, as a rule, do not have access to the complete food supplies of persons in temperate