94 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 60 



ure to cold per se, as is shown by the experience of arctic explorers, 

 sailors, shipwrecked passengers, etc. 



We have very great inherent powers of withstanding exposure 

 to cold. The bodily mechanisms become trained and set to maintain 

 the body heat by habitual exposure to open-air life. The risk lies in 

 overcrowding, so that infection becomes massive, and in overheating 

 our dwellings and overclothing our bodies, so that the mechanisms 

 engaged in resisting cold become enfeebled and no longer able to 

 meet the sudden transition from the warm atmosphere of our rooms 

 to the chill outside air of winter. The dark and gloomy days of 

 winter confine us within doors and, by reducing our activity and 

 exposure to open air, help to depress the metabolism ; the influence 

 of smoke and fog, diet, gloom of house and streets, cavernous places 

 of business, and dark dwellings, intensifies the depression. The 

 immunity to a cold after an infection lasts but a short time. When, 

 after the summer holidays, children return to heated schoolrooms and 

 to damp, chill autumn days, infection runs around. 



The unpleasant smell of crowded rooms is sensed only by new- 

 comers; and by them for only a short time after entering such rooms. 

 Most men, for example, sailors, are quite indifferent to this smell 

 and regard it no more than they regard tobacco smoke. Offensive 

 trade smells are unnoticed by the workers in such trades. The smell 

 nauseates sensitive educated people largely because they have been 

 taught to believe that the smell indicates the existence of an organic 

 chemical poison. A century or so ago, sick people went to breathe 

 the air in crowded school-rooms on the fanciful supposition that the 

 breath of the young and vigorous would heal their sickness. Pos- 

 sessed of such a fancy, the consumptive felt no nausea or loathing 

 of the smell but breathed in the close air with faith and hope. The 

 evidence of other workers and the experiments detailed in this paper 

 make it certain that there is no chemical volatile poison in the ex- 

 haled air. 



The history of hospital gangrene and its abolition by the aseptic 

 methods of Lister, as likewise the history of insect-borne disease, 

 show the great importance of cleanliness in crowded and much occu- 

 pied rooms. The essentials required of any good system of ventila- 

 tion are, then: (i) movement, coolness, proper degree of relative 

 moisture of the air, and (2) reduction of the mass influence of 

 pathogenic bacteria. The chemical purity of the air is of very minor 

 importance and will be adequately insured by attendance to the 

 essentials. 



