ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 267 



and chill in the body, especially when feeble or fatigued, are main fac- 

 tors. As in so many other maladies, the specific cause in rheumatic 

 fever may be the entrance of a micrococcus or other germ by means of 

 a chill, either in hot or cold weather. An inquiry into the distribution 

 of rheumatism, with regard especially to soil, climate, air, and dwell- 

 ings, and eliminating as far as possible predisposing human habits, 

 would furnish results of much value. There is some indication, as in 

 the case of malaria, that air near the ground in low places has much to 

 do with the incidence of the disease. Damp dwellings and clothes 

 conduce to an attack, and to the chronic form. It seems very probable 

 that it would be found that persons removed from ground air, as in the 

 attics of high buildings, are exempt from attack, except through food 

 and drink. 



MEASLES AND WHOOPING- COUGH. 



Measles and whooping cough are spread chiefly through the air to 

 persons in the immediate neighborhood of the sick, and of articles, 

 especially clothing, which have been exposed to the infective matter. 

 Segregation, ventilation, and avoidance and disinfection of materials 

 which may disseminate the disease are effective in prevention, where 

 they can be carried out. In the early stage of measles, as of influenza, 

 even while the symptoms are slight, the germs of the disease may infect 

 through the air, and therefore measures of precaution are difficult. The 

 best preventives against widespread and severe attacks are habitual 

 regard for sufficient air space and warmth and immediate isolation. 



DENGUE. 



Dengue is a disease somewhat resembling influenza in its symptoms, 

 but prevalent only as an occasional epidemic in tropical countries. It 

 is apparently spread by infection in the air from case to case, but not 

 through the general atmosphere. The reason of its failure to extend 

 beyond hot climates is quite obscure, but it would seem as if it required, 

 like yellow fever, a high temperature outside the body in order to grow 

 and disseminate germs fitted for infection. 



SMALLPOX. 



Smallpox has been ascertained by several careful investigations to 

 be capable of passing through long distances, at least half a mile or 

 a mile, of fresh air without losing its power of infecting susceptible per- 

 sons. The experience of hospitals in London and Paris is well known. 

 Recent observations on the spread of smallpox from a hospital near 

 Leicester, containing 49 patients, showed that a number of cases which 

 occurred in a suburb about 300 yards distant were in all probability due 

 to transport by the wind. The epithelial scales and dust of smallpox 

 cases are rather peculiarly protected from atmospheric influences, and 

 the conditions of the survival of exposed germs need inquiry. 



