DISTRIBUTION OF DISEASES. It is generally known that local conditions, such as climate, variation of temperature, the composi tion of the soil, elevation of the land above the sea-level, distribution of water, and the character of the vegetation, combine with the peculiar habits of the people to determine the greater or less prevalence of certain diseases in the dilrervnt regions of the earth. The science of no,ography in tins aspect did not receive much attention !a fore the beginning of the nineteenth century. and is still comparatively undeveloped. The impor tanee of climate as a factor in the distribution of diseases is obvious. Yet certain diseases, as Egyptian ophthalmia, the pellagra of Lombardy, the !Jeri-heti of Ceylon and the Malabar coast, and the elephantiasis of the Indian peninsula, ap pear to have no relation to climate, but are con fined to certain well-defined districts. Tropical regions are the home of malarial fevers, cholera. and hepatic diseases. This is due in part to the damp soil and decaying vegetation, particularly in the river valleys. The yellow fever of the Mexiertn Gulf, thongh often aggravated by other conditions, doubtless originated primarily front this cause. In the more temperate zones, typhus, typhoid, intermittent, and scarlet fever, are found. They are. however, for the most part, not ,o much endemic as epidemic. In the North ern Hemisphere. north of the tropical zone. ca tarrhal diseases prevail, while in the correspond ing zone of the Southern Hemisphere they are unknown. Intestinal catarrh prevails, however, to a considerable extent in some parts of the intertropical regions. in some cases, hilly regions are ravaged by fevers, while in the inter vening valleys fevers seldom occur. The cultiva
tion of the soil sometimes essentially modifies the character of the malarial diseases. The destruc tion of forests often results in the introduction of diseases unknown before. Indeed, as a gen eral rule, living vegetation tends to preserve health, while decaying vegetation is a prolific source of disease. Defective drainage, natural or artificial, is also a common source of disease, especially in cities. The personal habits of races and communities in respect to diet and cleanli ness• exert a wide influence upon the public health. Europe. on the whole. possesses the requisite condition, of health in greater perfec tion than any other quarter of the world. The rates of mortality from diseases of the lungs are greater in northern than in southern latitudes. This is illustrated by the prevalence of consump tion in the northeastern portion of the United States. Fevers art' um-re prevalent in the South ern than in the Northern States. Malarial fevers are especially fatal in the southern regions of the country: they are infrequent, however. where pine forests abound.
Consult: Annesley. ID into the Causes of DiseaSt s in India (London. I5551: Martin, Influf.nre of Tropical Climatts on European Con stitutions (London. 1577); Manson, Tropical s ( Loud, al. 11100) ; Twining. Clini•al 1 !last rat ions of llu .hurt Important Disca:es of ,?9?•1 and I 'a lc tills (London, 1 ; 11, ad, B. on 111C of India Loll.
dun. I. The older literature of medical gl. graphy int hides the excellent works of Altiliry and Vondet. Incidental illustrations of tion n ay be found nods r ENDENIIC: ; and in the articles on fever...