722 
CHEMISTR Y OF RESPIRA TION. 
Volume of an 
Air expired in 
CO 2 expired in 
Hour of Da j*. 
Respirations 
Expiration. 
One Minute. 
One Minute. 
Percentage of 
CO, in the 
per Minute. 
Expired Air. 
C.c 
. (37° and 75S Mm.). 
9 A.M. . 
12-1 
503 
6090 
264 
4-32 
10 „ . 
11-9 
529 
6295 
282 
4-47 
11 ,, . 
11-4 
534 
6155 
27S 
4-51 
12 noon . 
11-5 
496 
5578 
243 
4-36 
Dinner. 
1 P.M. . 
12-4 
513 
6343 
276 
4-35 
2 
13-0 
516 
6799 
291 
4-27 
3 ',', . 
12-3 
516 
6377 
279 
4-37 
4 „ . 
12-2 
517 
6179 
265 
4-21 
5 ,, . 
11-7 
521 
6096 
252 
4-13 
6 ,, . 
11-6 
496 
5789 
238 
4-12 
7 „ . 
11-1 
489 
5428 
229 
4-22 
upon the organism by long-continued habit — a day of work, a night of 
rest. This explains the persistence of the daily variation in metabolism, 
temperature, pulse, and respiration observed in an animal kept at rest 
and without food. 
The effect of light in increasing the respiratory exchange is pro- 
bably to be attributed chiefly to the increased muscular activity of most 
animals in the light. 1 
The influence of age upon the respiratory exchange. — The 
respiration of the foetus is relatively small, and this condition, within 
certain limits, persists for a short time after birth. The estimation, 
however, of the effect of age upon the respiratory exchange is not so 
simple as it at first appears, for there are two factors which have to 
be taken into account. In the first place, the young animal has a 
relatively greater surface in proportion to its mass than the adult 
animal, and this causes a more rapid respiratory exchange ; in the 
second place, young animals of different species are born in different 
degrees of development. A newly -born guinea-pig is covered with fur, 
has its eyes open, and is able to run about and feed ; whereas a newly- 
born rabbit, rat, or mouse is naked, blind, and helpless. A similar 
contrast is observed in the condition of the newly-hatched chick and 
pigeon. Elsewhere it has been shown that newly-born mammals and 
birds can be arranged in two classes — those which can and those which 
cannot maintain their temperature ; and there is a similar contrast in 
the effect of changes of external temperature upon their respiratory 
exchange. These factors must, therefore, be remembered in estimating 
the effect of age upon the respiratory exchange. 
In the case of man, experiments have been made by Andral and 
Gavarret, 2 but it is difficult to estimate the influence of the ratio 
between mass and surface of the body, for the weights of the subjects 
are not given. In the following table are some of Scharling's 3 results, 
which show that, weight for weight of body, the child discharges more 
carbon dioxide than the adult : — 
1 Numerous references to the controversy on this point will be found in a paper by 
Fubini and Benedicenti, Arch. ital. de biol., Turin, 1891, vol. xvi. p. 80. 
2 :; Recherches sur la quantite d'acide carbonique exhale' par le poumon dans l'espece 
humaine," Paris, 1843. Extract in Ann. de chim. etphys., Paris, 1843, Ser. 3, tome viii. 
s Ann. d Chcm. u. Pharm., 1843, Bd. xlv. S. 214. 
