CLIMATE IN SOME OF ITS RELATIONS TO MAN 257 



Winter and Summer Diseases of the Temperate Zones. — It is nat- 

 ural that such marked seasonal and such sudden weather changes as 

 ours should be reflected in the character, distribution and frequency 

 of the diseases which are found in these zones. Diseases of the respira- 

 tory system, bronchial and rheumatic affections, diseases that result 

 from colds and chills, pneumonia, bronchitis, influenza, diphtheria, 

 whooping cough, are all common in climates with sudden marked tem- 

 perature changes, especially if these changes are accompanied by cold, 

 damp winds. These diseases are also most frequent in the winter 

 months, when the weather changes are more common and more severe, 

 and when, in consequence, the vitality of the body is lowered and its 

 power of resistance against the attack of the disease germs is weakened. 

 A greater prevalence of diseases of the respiratory system, catarrhs and 

 rheumatic affections in cool, moist weather, with sudden changes, has 

 been shown by Weber, and several investigators have found a higher 

 mortality after a greater variability of temperature. Many contagious 

 or infectious diseases, such as diphtheria, influenza, measles and scarlet 

 fever, for example, are also more common in the colder season, not 

 because the lower temperatures are the direct controlling factor, but 

 largely because the colder weather drives people indoors; houses and 

 buildings generally are less well ventilated; more clothing is worn, less 

 attention is paid to personal cleanliness and there is increased oppor- 

 tunity for contagion, especially among the poorer classes. Obviously, 

 these are indirect effects of meteorological conditions. 



In the warmer months, fevers and diseases of the digestive system, 

 diarrhoea, malaria, typhoid fever, are prevalent. Thus there are usually 

 two maxima of mortality: one in the colder season, when the change- 

 ableness of temperature is greatest, chiefly due to respiratory diseases, 

 and another in the warmer months, largely due to infant mortality 

 from disorders of the bowels. 



Climate and Man: General. — Let us turn now to some larger, more 

 general, relations of climate and man. Man's climatic environment 

 affects him in many ways. His clothing, dwellings, food, occupations 

 and customs; his physical and mental characteristics; his systems of 

 government; his migrations; his history — all are affected to a greater 

 or less degree. 



Civilized man protects himself more or less successfully against 

 unfavorable climatic features. Thus, there is a gradual transition from 

 the primitive shelter made of branches of trees, of skins or leaves, to 

 the permanent and highly elaborate modern building, which is both 

 heated and cooled artificially. There is also a transition from the 

 primitive and scanty clothing made of leaves or bark, where trees grow, 

 or the skin of an animal, where trees are lacking, or where warmer 

 clothing is needed, to the manufactured or perhaps imported garment 

 of wool, cotton or silk. Again, there is the increasing variety of food, 



VOL. LXXVI. 18. 



