OXYGE-N CONSUMED AND CARBON DIOXIDE EXHALED 153 



70 F., it is found that air inspired through the nose and ex- 

 pired through- the mouth has its temperature raised from 70 

 to about 95 ; the rise is less when the inspiration takes place 

 through the mouth. The last air of expiration is warmer 

 than the first. This gain of heat while the air is in the lungs 

 needs no explanation when it is remembered that the aver- 

 age temperature of the tissues with which it is in contact is 

 98.5 F., or higher. 



(d) Gain of Water. This water is in the form of vapor. 

 It is natural that the air should absorb water from the moist 

 surfaces with which it is in contact. The capillary network 

 with which it is in close relation supplies moisture to the mu- 

 cous membrane not only of the alveoli but of the entire 

 respiratory tract. One or two pounds of water are elimi- 

 nated thus daily. 



(e) Gain of Ammonia. Ammonia is exhaled in small 

 quantity by the lungs. It is insignificant except in cases of 

 suppressed kidney action. 



(/) Gain of Organic Matter. The quantity of organic 

 matter exhaled by the lungs is inconsequential (unless venti- 

 lation be bad), but such exhalation does occur to a small ex- 

 tent. It gives the odor to the breath. 



(g) Gain of Nitrogen. The exhalation of this gas by the 

 lungs is of no respiratory importance. The amount is said 

 to be Moo4o the amount of oxygen consumed. An occa- 

 sional loss of nitrogen has been observed. 



(h) Decrease of (Actual) Volume. When the external 

 temperature is below about 90 F. the volume of expired air 

 is a little greater than that of the inspired air, because of the 

 increase of temperature it undergoes in passing through the 

 lungs. But the actual volume of the expired air, when re- 

 duced to the same temperature as the inspired, is found to be 

 always a little less than that of the latter. It is estimated 

 that from #o-%o of the total volume of the inspired air is 

 thus lost in respiration. 



Besides the substances mentioned as being exhaled from 



