THE STORY OF THE LUNGS, SKIN AND KIDNEYS 83 



physical welfare may be conserved. The story of the 

 Black Hole of Calcutta is familiar to all. The results 

 of breathing and re-breathing foul and fetid air con- 

 taminated by the waste products of human beings, 

 received on that occasion an object lesson of histori- 

 cal kind. Other incidents have occurred to show the 

 marked influence which a highly polluted atmosphere 

 exercises in inducing effects of a serious nature 

 leading to ill-health, and in extreme cases to death. 

 Whatever difficulties exist in the way of procuring fresh 

 air, it is at least something to realise its importance 

 in the maintenance of health. One of the reasons 

 for the large amount of public apathy which exists 

 regarding the necessity for securing a pure air sup- 

 ply, is due to the fact that the effects of breathing 

 polluted air are generally slow and insidious in their 

 action on the body. We rapidly become accustomed 

 to a foul atmosphere, and thus fail to appreciate the 

 harm which is being done by our inhaling it. The 

 experiment of Claude Bernard is well worth bearing 

 in mind in connection with this topic. He placed a 

 sparrow under a bell jar of a size calculated to con- 

 tain sufficient air to keep the bird alive for three 

 hours. At the end of the second hour a fresh 

 sparrow was introduced into the jar, this second bird 

 at once collapsing and dying on account of the im- 

 purity of the atmosphere produced by the first bird, 

 but amidst which atmosphere the latter could live for 

 another hour. This experiment, it is true, does not 

 find its exact counterpart in humanity, but none the 

 less is the grave lesson taught us that a supply of 

 pure air is even more necessary for the preservation 

 of health than pure food and pure water, in respect 

 at least, that we are always breathing, whilst we are 

 not perpetually eating and drinking. 



