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CHZMISTR Y OP RESPIRA T10N. 



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. dc bioL, Turin, 1891, vol. xvi. p. 80. 



2 "Recherches sur la quantite d'acide carbonique exhale par le pounion dans 1'espece 

 hiunaine," Paris, 1843. Extract in Ann. de chim. et phys., Paris, 1843, Ser. 3, tome viii. 



3 Ann. d Chem. u. Pharm., 1843, Bd. xlv. S. 214. 



