144 THE POPULAR SCIENCE MONTHLY. 



sionaries against the use of animal food, and warned them that it would 

 produce a disease which, like original sin, could only be cured by bap- 

 tism, i. e,, frequent shower-baths and invocations of the Great Spirit ; 

 and Bernal Diaz tells us that the subjects of Montezuma were afflicted 

 with an eruptive disease, more painful though less incurable than lep- 

 rosy, but that fevers made their first appearance with the Spaniards, 

 and were long limited to the district of Toltepec (in the valley of 

 Anahuac) and the Spanish quarter of the city of Tlascala. 



In our cotton States, too. Baton Rouge, Vicksburg, and Memphis, 

 on their high and dry bluffs, and Chattanooga, at an elevation of seven 

 hundred feet above the level of the Gulf, have suffered more in propor- 

 tion to their population than any place this side of Vera Cruz; while 

 the swamps of the Red River and the Arkansas bottom-lands had not 

 much to complain of besides their chronic " chills," and the ne-plus- 

 ultra swamp, called Florida, has been entirely spared. 



It is also known that the miasmatic virulence of alluvial districts is 

 aggravated by excessive moisture and diminished by dry seasons, espe- 

 cially long, dry summers, which convert festering bogs into harmless 

 steppes, and confine the swamp-belt of large rivers to a narrow strip 

 along the lower shores. Now, if yellow fever, typhus, and cholera, 

 were depetiding upon what physicians call telluric causes, i. e., the con- 

 dition of the soil, in our more or less immediate neighborhood, wet years 

 would be the most dangerous, whereas experience shows that, on the 

 contrary, epidemics generally follow upon dry, hot summers, like the 

 last and those of 1873 and 1868. These facts, which agree with the 

 experience of the remotest countries and times, only confirm what die- 

 tetic reasons might indicate a 2^riori, viz., that the so-called zymotic 

 diseases have subjective rather than objective causes : they are pro- 

 duced by the unhealthy condition, not of the country so much as of 

 the inhabitants, and originate in dry cities oftener than in swampy 

 forests. 



During the long centuries of the Juventus 3Itmdi, forests and 

 swamps were almost synonyms, as they still are in the lower latitudes 

 of America and Eastern Asia. Animal life swarms and revels in such 

 regions. Herbivorous and carnivorous animals, and our cousins the 

 anthropoid apes, thrive in the moist woodlands of the torrid zone, and 

 the Asiatic Malays, the natives of Soodan and Senegambia, and the 

 aborigines of our own continent, have inhabited the swampiest dis- 

 tricts of the tropical bottom-lands for ages with perfect impunity. 

 They do not employ any of the antidotes by which the stranger hopes 

 to secure himself against what he calls climatic influences, and that 

 their immunity is not the inherited privilege of a special race is demon- 

 strated by the diseases of the Mexican Indians, who have adopted the 

 diet of their Spanish masters, and of the West African negroes, who 

 have been carried to the far less swampy islands of the West Indian 

 Archipelago. Dietetic differences alone can, therefore, furnish a logical 



