284 ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 



the possibility of the revival of plague through irrigation can not be 

 lost sight of. What malaria means in India is best realized by a glance 

 at the mortality statistics, which show that 3,000,000 natives annually 

 fall victims to this most fatal of all endemic diseases, and we know 

 that where one dies many are enfeebled for life. 



Looking at the available evidence, we may fairly infer (1) that the 

 inhabitants of temperate climates are, on the whole, intellectually and 

 physically superior, and that they owe this position largely to atmos- 

 pheric conditions; (2) that in the tropics and commonly in the temper- 

 ate zone the inhabitants of the mountains are physically the strongest; 

 (3) that tropical countries are not favorable for rapid permanent coloni- 

 zation by the races of northern Europe and of the Northern States of 

 America; (I) that the maintenance of healthy conditions in persons 

 passing from one kind of climate to another very different climate 

 depends to a great extent on the observance of hygienic method and a 

 change of habit, but also on the time taken to make the move, rapidity 

 of transition being inimical to health; (5) that tribes or races have 

 moved from hot to cold, and cold to hot climates, occupying centuries 

 or thousands of years in their progress, and have not invariably suf- 

 fered or degenerated, and that therefore, and on other grounds, it is 

 probable that fairly healthy hot or cold countries may in the course of 

 centuries be colonized by races which have successively and slowly 

 occupied lauds warmer or colder than their own; (0) that people long 

 subject to extreme variations of temperature, as between winter and 

 summer, and day and night, are better able to colonize than those who 

 are subject to more uniform temperature. 



MODE OF ATTACK OF MIASMATIC DISEASES. 



It is very desirable that the various diseases which affect the inhabit- 

 ants of moist countries in the tropics should be traced to their original 

 haunts, and their favorite channel of communication be ascertained. 

 Is the condition known as tropical anaemia mainly a result of tempera- 

 ture or of an emanation from the soil in the air? Are dysentery, diar- 

 rhea, hepatitis, and liver disease due mostly to organisms swallowed 

 in food or drink, or inhaled in the air overlying soil rich in organic 

 matter, or are they produced by merely physical properties of the 

 atmosphere acting on imperfectly healthy bodies, by means of over- 

 fatigue, insolation, or chill 1 It appears likely that both air and water 

 are capable, in the case of several tropical diseases, of conveying the 

 poison. Thus, at Sierra Leone, improved water lowered the death rate, 

 but it still remains high; in the villages of the ISTajagarrh hills in India, 

 a drain-cut reducing the flood level by 3 feet greatly improved the 

 health of the people, and splenic enlargement cases were reduced to 

 less than one-sixth of their former prevalence; in the canal -irrigated 

 country in India fever.is both more prevalent and more virulent, and a 

 great difference in the health of the people is observed between places 



