VII.

Thus it appears how important is the function of respiration, and how vital the necessity for pure air.

Pure dry air contains about 21 gallons of oxygen, and 79 gallons of nitrogen out of 100, and about one gallon of carbonic acid out of 2500. Man will consume, on the average of 20 respirations a minute, or 1200 respirations the hour, about 20 pounds of air, and give off 2-1/2 pounds or more of carbonic acid, besides half a pound of watery vapor, per diem, or, according to Andral and Gavaret, 22 quarts of carbonic acid per hour. We have shown in the chapter on Alimentation how this process of respiration affects the nutrition, and how serious the results of its disturbance. The purer the air, the more perfect the type of men and animals. This was understood by the ancients, and they established their most famous schools for gladiatorial training at Capua and Ravenna.

The same law is observed at the present day by the admirers of the race-horse. The purity of the air gives purity to the blood, and the blood builds up the system in like proportion of excellence.