1 88 



QUANTITY OF GASES EXCHANGED. 



respiratory passages, so that the volume of the expired air is one-ninth greater 

 than the air inspired. 



8. A very small quantity of ammonia is found in the expired air = 0'0204 

 grammes in 24 hours ; it is probably derived from the blood. 



9. Small quantities of H and CH 4 are expired, both being absorbed from the in- 

 testine. In herbivora, Reiset found that 30 litres of CH 4 were expired in 24 hours. 



125. QUANTITY OF GASES EXCHANGED. As under normal circum- 

 stances more O is absorbed than there is C0 2 given off (equal volumes of O and 

 C0 2 contain equal quantities of O), a part of the O must be used for other oxida- 



tion-processes in the body. According to the extent of these latter processes, 

 ratio of the O taken in to the C0 2 given out- 



^- 0-906 nffl 



the 



rmally ) 



must vary. 



The amount of C0 2 given off may be less than the " mean " above stated. The 

 quantity of C0 2 alone is not a reliable indication of the entire exchange of gases 

 during respiration ; we must estimate simultaneously the amount of absorbed 

 and the C0 2 given off. 



126. DAILY GASEOUS INCOME AND EXPENDITURE : 



Income in 24 hours. 

 Oxygen 



744 grms. = 516*500 c.cmtr. ( Vierordt). 



(At C. and mean barometric pressure.) 



Expenditure in 24 hours. 

 Carbonic Acid 



900 grms. = 455500 c.cmtr. ( Vierordt). 



36 grms. per hour (Scharling). 



32-8 to 33*4 grms. (Liebermeister)* 

 34 grms. . . ,, . (Panum). 



31 *5 to 33 grms. . ,, . (Ranked 



Water 640 grms. . . . ( Valentin). 



330 ,, . . . (Vierordt). 



127. CONDITIONS INFLUENCING THE GASEOUS EXCHANGES. The 



formation of C0 2 , in all probability, consists of two distinct processes. First, com- 

 pounds containing C0 2 , which are oxidation-products of substances containing 

 carbon, seem to be formed in the tissues. The second process consists in the separa- 

 tion of this C0 2 , which, however, takes place without the absorption of O. Both 

 processes do not always occur simultaneously, and the one process may exceed the 

 other in extent. The formation of C0 2 is affected by : 



1. Age. Until the body is fully developed, the C0 2 given off increases, but it 

 diminishes as the bodily energies decay. Hence, in young persons the O absorbed 

 is relatively greater than the C0 2 given off ; at other periods both values are pretty 

 constant. Example : 



The absolute amount of C0 2 given off is less in children than in adults ; but if 

 the C0 2 given off be calculated with reference to body-weight, then, weight for 

 weight, a child gives off twice as much C0 2 as an adult. 



2. Sex. Males, from the eighth year onward to old age, give off about one- 



