EESP1KATION. 151 



On the ether hand, fatigue, depression of spirit, grief, and 

 anxiety diminish the frequency of respiration. 



343. The lungs of a man of average size, and in usual 

 health, when at rest, when neither expanded nor contracted, 

 will hold two hundred and ninety cubic inches, or a little 

 less than a gallon of air. But, when distended by ordinary in- 

 spiration, they receive twenty inches more. This will make 

 three hundred and ten inches when full. This twenty 

 inches is the usual extent of respiration. This is the amount 

 of air which the lungs need, and which they receive at every 

 inspiration, when allowed freedom of motion, eighteen times 

 a minute, and one thousand and eighty times an hour. 



344. This quantity of pure air is not merely wanted to fill 

 the capacity of the chest and lungs, but it is needed for the 

 purification of the blood. Bearing in mid that the blood 

 receives from the system carbon and hydrogen of which it 

 must be relieved; and knowing that it receives with the 

 chyle more water than is wanted ; and that, when these are 

 combined, they go to the lungs to be disburdened of their 

 superfluous and noxious elements; it is natural to sup- 

 pose that the amount of air should correspond with the 

 quantity of these matters, which are thus to be removed. 



345. Then in order that the air may meet the wants of 

 the blood, the size of the chest corresponds to that of the 

 body, and the motions of the ribs and the expansion of the 

 lungs correspond to the flow of the blood. This one would 

 suppose to be the case from a mere general view of the har- 

 monies of nature; for the Creator makes all his works con- 

 sistent one with another. 



346. The quantity of blood in the whole system of a man 

 of average size, amounts to about twenty-eight pounds. 

 ( 232, p. 107.) The heart beats in a man about seventy-five 

 times a minute, and forces out of itself about two ounces, or 

 half a gill, at each pulsation or contraction ; and, consequent- 

 ly, in one minute, more than nine pints of blood are sent 

 to the lungs to be acted upon by the air. In the same time, 

 twelve pints of fresh air are brought into the lungs ; arid 



