These statistics do not entirely support the declaration of Hippocrates that "races are the daughter of climates," but tend to show that the vital resistance of the different races in tropical climates depends more on external conditions than on race. Acclimatibility of strong, healthy, adult Europeans of both sexes in tropical climates must be admitted without any reserve, provided that they assiduously observe all hygienic rules. Stokvis disproves the allegation that the European is not able to produce in tropical regions more than three or four generations of true European blood, and that from the third or fourth generation onward sterility is the rule. So accustomed, remarked Felken, however, is a man to his environment that it is difficult to remove an European from his home in the temperate region to any other, and yet for him to retain his health. Much may be done in the tropics to render climate more salubrious and sanitary precautions will do a great deal for the health of the community. But when all is done permanent residence for Europeans under European conditions is out of the question in the low-lying regions of the tropics. Comparatively few areas exist in the tropics where any great success for European colonisation can be prophesied from altitude alone. The influence of altitude on the physiologic characteristics is, however, very evident. The residents at high altitudes are strong, robust, buoyant, and of great mental and physical endurance. In disproof of this position of Felken, Viault, of Bordeaux, has shown that the phenomena resultant on the acclimation of man at great altitudes comes neither from the frequency of respiratory movements nor from greater activity of the pulmonary circulation as has been asserted, but from increase of red blood globules. While the effects of both excessive heat and excessive cold may be admitted, even there other factors play a part. Very high mean temperature with low humidity is more likely to result in sunstroke and allied conditions than high temperature with high humidity. Low temperature of the Arctic regions tends to produce anæmia in natives of temperate zones. Food and depressing circumstances have, however, to be taken into consideration.