ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 241 



The greater part of the dust of clean habitations, consisting of motes 

 derived from mineral, vegetable, and animal substances, has little 

 apparent effect upon health. But it certainly tends to reduce vitality 

 by some small amount, and gives extra work to the breathing organs. 

 Consequently, to invalids and delicate persons it is important to reduce 

 this dust by all reasonable means. A beam of strong light, sunlight 

 or the electric lamp, shows the air of most inhabited rooms to be so 

 crowded with dust as to be almost opaque to vision. Aitken found 

 41,000,000 particles in the cubic inch in a room where gas was burning. 

 Rooms with polished wooden floors, painted hard plaster, glazed paper, 

 or wood-paneled walls, aud not containing fluffy fabrics, evolve much 

 less dust. They are more healthy not only on this account, but chiefly 

 because they provide much less pabulum and protection for the growth 

 of noxious microorganisms. 



De Ohaumont found in the air at Paddington and in University Col- 

 lege Hospital particles composed of the epidermis of hay, of pine wood, 

 linen, cotton, epithelium, charred vegetables, and minerals. 



Tichborne, of Dublin, found in a street 45.2 per cent of organic matter, 

 and at the top of a pillar 29.7 per cent. Most of it was finely ground 

 manure. 



The spores and mycelium of Achorion schonleinii and of Tricophyton 

 tonsurans have been found in the air of a hospital for diseases of the 

 skin. 



The surface of the ground in streets, squares, courts, and gardens, 

 and the sweepings of dwellings and stables,' contain swarms of the 

 germs of the bacillus of tetanus, a disease fatal to man. These chiefly 

 infest the droppings of various domestic animals, and may be carried 

 through the air to wounds; commonly they infect by contagion and 

 not through the air. Drying, light, and putrefying matter do not kill 

 the bacillus, nor does a temperature of 80° to 90° C. Tetanus has 

 caused great mortality among soldiers who have lain wounded at night 

 on the field of battle, probably owing to the lifting of the bacillus by 

 emanations from the ground and its deposit on open wounds. 



SEWER AIR. 



Sewer air contains molds, fungi, bacteria, and animal and vegetable 

 debris. The microbes do not exceed about 6 per liter in a good sewage 

 system. In ordinary drains, however, they are much more numerous, 

 and are borne into the interior of houses in company with highly 

 poisonous gases. The gases of sewers are sulphuretted hydrogen, 

 ammonium sulphide, carbon bisulphide, a very little marsh gas, com- 

 pound ammonias, with traces of ptomaines and leucomaines. 



AIR OF MINES. 



The air of mines contains only a few molds, fungi, and bacteria. 

 SM 95 10 



