EFFECTS OF RESPIRATION OF A VITIATED ATMOSPHERE. 411 



perhaps of typhus fever, is associated with decomposing decrements, which 

 have either dried and then having become reduced to a pulverulent form 

 float in the air, and are taken into the system by the lungs, or are held in 

 suspension in water, and are thus introduced into the body. The remarka- 

 ble experiments of Tyudall and of Cunningham demonstrate iucoutestably 

 that a large number of organic particles are constantly floating in the air, 

 some of which are probably the germs of infectious disease which only re- 

 quire a favorable soil on which to germinate. In all large towns difficulty 

 is experienced in the removal of excremeutitious matters ; cesspools, which 

 are primitive means of disposing of such material, cannot be permanently 

 used in large towns, though they are still far too commonly employed. 

 Even direct draining into the sea, unless the sewers are carred out for a 

 very long distance, has been found ineffective, the water near the shore soon 

 becoming fetid and impure. When an extensive system of drains, as in 

 London, is in operation, fresh and unlooked-for dangers arise: the houses 

 warmed in winter constitute so many flues, which suck up the foul air of 

 the cooler drains, and typhoid fever in a more or less virulent form makes 

 its appearance. The adoption of earth-closets, though practicable in country 

 districts, is inapplicable in town. Probably little improvement will be made 

 for a long period to come upon the plan which is now becoming general in 

 London, of an unlimited water supply to each house, the water flowing into 

 drains which conduct the fluid to a distance of several miles, where having 

 discharged itself into large tanks, it is deodorized, and then applied to the 

 fertilization of the surrounding soil. Petteukofer has recently drawn atten- 

 tion to the importance of investigating the condition of the soil air as well as 

 of the soil or ground water, in all investigations on the origin of zymotic 

 diseases : he has shown that a few feet under the surface there is already as 

 much carbonic acid as in the worst ventilated human dwelling-places. This 

 quantity increases with the depth, so that at 156 inches there is more than 

 at 58 inches, all the year round, except during the months of June and July, 

 when an inverse proportion arises. He attributes its formation to organic 

 processes taking place in the soil, which demand further investigation. 



328. Of the remarkable tendency of the respiration of an atmosphere 

 charged with the emanations of the Human body, to favor the spread of 

 zymotic diseases, a few characteristic examples will now be given : The 

 dwellings of the great bulk of the population of Iceland seem as if con- 

 structed for the express purpose of poisoning the air which they contain. 

 They are small and low, without any direct provision for ventilation, the 

 door serving alike as window and chimney ; the walls and roof let in the 

 rain, which the floor, chiefly composed of hardened sheep-dung, sucks up ; 

 the same room generally serves for all the uses of the whole family, and not 

 only for the human part of it, but frequently also for the sheep, which are 

 thus housed during the severer part of the winter. The fuel employed in 

 the country districts chiefly consists of cow-dung and sheep-dung, caked and 

 dried ; and near the seacoast, of the bones and refuse of fish and sea-fowl ; 

 producing a stench, which, to those unaccustomed to it, is completely insup- 

 portable. In addition to this, it may be mentioned that the people are noted 

 for their extreme want of personal cleanliness ; the same garments (chiefly 

 of black flannel) being worn for months without being even taken off at 

 night. Such an assemblage of unfavorable conditions, combined with the 

 cold, damp nature of the climate, might have been expected to induce tuber- 

 cular diseases of various kinds ; but from these the Icelanders appear to 

 enjoy a special exemption ( 66, iii). Syphilis, also, is wanting, or nearly 

 so ; and yet, notwithstanding that the number of births is fully equal to the 

 usual average, the population is stationary, and in some parts actually dirniii- 



