282 BIOLOGICAL PROBLEMS 



clothing. This odour can but have a transient psychic 

 effect upon those who first enter an already stuffy 

 room for our very keen sense of odour is rapidly 

 exhausted. 



Certain other changes in fouled air had, until com- 

 paratively recently, received but little consideration. 

 I refer to the fact that air markedly fouled by human 

 occupation of a room becomes changed in its physical 

 characters; it is more or less stagnant, its humidity is 

 high, and its temperature considerably increased. 

 Experimentation was therefore directed to test the 

 power of the altered physical state of the atmosphere 

 to produce the enervating effects of overcrowded and 

 badly ventilated rooms. The experiments have gene- 

 rally consisted in confining men in comparatively 

 small experimental chambers and observing the effects; 

 and, later, certain contrivances were adopted for vary- 

 ing the quality and the quantity of the air within the 

 chamber. Sometimes tubes leading from the chamber 

 to the outside air have been provided, and 'it was 

 found that when subjects were affected by the atmos- 

 phere of the chamber they obtained no relief by 

 breathing through this tube, whereas if they stepped 

 outside of the chamber relief came at once. Again, 

 if a subject breathes through a tube the stale hot air 

 of the chamber, while standing outside of it, no un- 

 pleasant symptoms appear. Even when sitting in 

 the chamber relief is experienced when the air is set 

 in motion by fans. These experiments have been 

 repeated, with slight modifications, by several inde- 

 pendent workers, and the results have always been 

 in strict conformity. They establish the fact that the 

 evil results of close, ill-ventilated rooms are not due to 

 respiratory impurities accumulating in the frequently 

 re-breathed air, but to its altered physical characters 

 1 in short, the evils of foul air are not dite to chemical 



