DANGERS AND PRECAUTIONS 



may result in permanent injury. 



Persons who suffer from sinus infection should not dive. The pressure 

 produces pain, and probably irritation which is harmful. 



It is well for those who contemplate diving to have a physical examina- 

 tion for there are other ailments and defects of the human system which 

 probably are irritated by subjection to compressed air. Above all, I be- 

 lieve that submarine diving should not be practiced by persons who do 

 not have an entirely normal heart condition. Our bodies are created to 

 function best under average conditions of living, yet they can resist ex- 

 tremes of temperature, privations and muscular effort to a most amazing 

 degree— provided the old heart is normal. Perhaps the greatest strain on 

 the heart is anything that interferes with breathing. The lungs take in 

 more or less oxygen by frequency of respiration which varies automati- 

 cally according to the needs of the body. When we run, or do any physi- 

 cal work, we breathe fast; when we sleep we breathe slowly. We live, 

 for the most part, surrounded by fresh air and, therefore, when we re- 

 spire at the rate of forty-four per minute, we feed ourselves with twice 

 as much oxygen as when we are breathing at twenty-two. The lungs do 

 their job so long as an excess of fresh air is available. This is not always 

 the case with the diver. Air is fed to him in measured quantities by a 

 man pumping. Sometimes he finds himself breathing rapidly and getting 

 no relief. This is because he is getting just so much air and it is not 

 enough. The rapidity of his respiration is of no help— each time he fills 

 his lungs he gets part fresh air and part foul. This causes distress and he 

 breathes still faster. The involuntary effort puts a strain on the heart to 

 which it should not be subjected if it is not in perfect condition. 



There is great variation in the quantity of air that the diver gets and 

 requires. If he is at maximum depth the pump must be operated faster 

 than if he is in shallow water. If he works at dislodging specimens he 



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