ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 277 



the open air, in islands to which no infection is brought by human 

 agency, and in well-ventilated institutions where every possible precau- 

 tion against infection from without can be rigidly maintained. Even 

 the Isles of Scilly, near the southwestern coast of England, were free 

 from measles, scarlet fever, and smallpox for ten years, the only district 

 exempt out of over seven hundred in the whole country. It was also 

 one of the seven districts in which no death from diphtheria occurred. 1 

 Since communication has become frequent, owing to a great increase in 

 trade, the immunity does not continue, and influenza broke out there 

 only a few weeks later than on the mainland. Another island, Alder- 

 nay, was affected early by influenza through the examination of goods 

 by custom-house officers, who caught the infection soon after the arrival 

 of the steamer. 



PREVENTION OF SPREAD AND PREVALENCE OF VARIOUS MALADIES. 



Prevention of the spread of these various classes of disease, the 

 reduction of some and the extinction of others, may be effected by 

 the following means: 



1. Malaria class. — Drainage, cultivation, planting, proper disposal of 

 refuse and carcasses. In places where a small area of moist ground or 

 small marsh gives off the dangerous exhalations, the surface might 

 be covered with a film of crude petroleum to prevent the escape of 

 the germs. Other experiments on the treatment of the surface of the 

 ground with antiseptic mixtures might lead to valuable results. 

 Powdered charcoal, and lime, might be tried. 



2. Cholera class. — Proper disposal of refuse, drainage of soil, cleanli- 

 ness and airiness of streets, houses, quays, ships; prompt disinfection 

 and cleaning of places where first cases occur; prevention of over- 

 crowding. Where any damp surface, as in a midden, pool, or drain, is 

 suspected of giving off dangerous emanations, crude petroleum might 

 have the effect of imprisoning the germs by an impervious film . Experi- 

 ments are needed on means for the exclusion of living organisms from 

 the air, where they are numerous, by treatment of the surface soil; also 

 on substances inhibitive of their growth, which might be used on a 

 large scale. 



3. Typhus class. — Cleanliness and good ventilation of dwellings and 

 of their surroundings and avoidance of overcrowding in houses, schools, 

 etc., prevent this class of disease from arising, but ordinary personal 

 infection has to be attacked also by isolation on the occurrence of the 

 first symptoms. The inside walls, floors, etc., should be of some imper- 

 vious material, easily and frequently washed. A dense cement or hard 

 wood maybe suitable; but, whatever the material, liberal ventilation 

 and cleansing are required to prevent deposition of organic matter and 

 growth of fungi. In schools, etc., the walls should be of smooth cement, 



1 Public Health Reports. Sir John Simou. 



