SUPREMEJ.Y IMPORTANT. 51 



exactly as the luiigs of all animals demand it. ;ind has taken the 

 most wonderful precautions to keep it so, and therefore she has 

 made no provision in the animal structure for straining or 

 purifying it in any way, before it comes in direct contact with the 

 blood. Consequently any animal can be far more easily injured 

 or destroyed by impure air, tlian by impure food or even w\ater. 



101. — According to Dr. Tanner's experience we can live 

 forty days without food : we know that we can live some days 

 without renewing the supply of water ; we cannot live five 

 minutes without a fresh supply of air. A horse or a man can 

 support action or thought with a great deficiency of food, but 

 any deficiency of oxygen will at once paralyse him. Let five 

 throbs of unoxyginated blood be sent to his brain, and the dray 

 horse could not move his own tail, and William Gladstone 

 could not repeat the alphabet. The most healthy children are 

 often those who get the least food and the most air. The little 

 rosy bird keeper wiio lives on a shilling a week in the open air 

 is often an object of surprise and envy to parents whose pale 

 pampered children are coddled up in ceiled rooms. We can eat 

 and drink enough to keep us going for twelve hours, we cannot 

 lay up one minute's store of oxygen ; we can run and jump when 

 hungry and thirsty, we can do neither when our lungs cannot 

 supply us with sufficient air. Excitement will make us forget 

 that we are hungry, no excitement will take us over a hurdle 

 when the weak knees tell us that the lungs cannot get oxygen. 



102. — We know very little about what life is. Three 

 hundred years ago physicians did not even know that the blood 

 circulated at all : now we know that it must come to every part 

 of the body, constantly loaded with heat and oxygen, and return 

 every minute or two to the lungs for a fresh supply, and that 

 the pace at which this can be done limits the amount of exertion 

 of which any warm blooded animal is capable. Still we do not 

 know all that it does in its constant round, nor can we point to 

 the exact reason why we cannot act or think a moment without 

 it, or why all increased bodily exertion demands a corresponding 

 increase in the supply of air to the lungs, and of blood and 

 oxygen to every part of the body. For our present purpose we 



