CHAPTER XVI 

 THE HYGIENE OF RESPIRATION 



WE have seen how dependent the animal organism 

 is upon the air as a source of oxygen and as a means of 

 getting rid of carbon dioxide and other volatile products 

 of the body's activity. In order to serve this purpose, 

 the air breathed must be both rich in oxygen and poor 

 in carbon dioxide. These conditions would be per- 

 fectly fulfilled, if we lived constantly in the open air. 

 The necessity of protecting ourselves from cold and wet, 

 and the consequent living in closed spaces, such as the 

 modern dwelling house, have, however, made it more diff 

 cult to get a constant and pure supply of air. Indeed, 

 in many cases, no attempt at all is made to get it. 



Effects of respired air. A study of persons who 

 constantly live and work in close rooms shows that they 

 are pale, weak, with poor appetite, and in a large per- 

 centage of cases, with marked tendencies to consumption, 

 whereas those who work out-of-doors are ruddy and 

 strong. Experiments on animals have also shown the 

 same results from breathing air made impure by respira- 

 tion. For example, a series of cages for mice was ar- 

 ranged with tight sides, so that the only air which 

 reached them came through one end of the series and 

 made its exit at the other. It was found that the ani- 

 mals in the first cages were perfectly well and strong, 

 while those in the others showed weakness and other 

 signs of poisoning, which increased in degree with their 

 distance from the source of the fresh air supply. In the 

 instance of the Black Hole of Calcutta, where a large 



182 



