528 OF RESPIRATION. 



of Chlorosis, has been already noticed ; in four cases recorded by Hannover, the 

 hourly expiration was 123.6, 118.6, 116.9, and 106.3 grains; the absolute quan- 

 tity diminishing as the respirations increased in rapidity. In chronic diseases of 

 the respiratory organs, as might be anticipated, the amount of Carbonic acid 

 exhaled undergoes a sensible diminution (Nysten 1 and Hannover 3 ). Further 

 researches are much needed on this subject ; but, for obvious reasons, they cannot 

 be readily made in severe forms of disease. 



f. Muscular Exertion or Repose. The effect of bodily exercise, in moderation, 

 is to produce a considerable increase in the amount of carbonic acid exhaled, 

 both during its continuance, and for some little time subsequently to its cessa- 

 tion. According to the observations of Vierordt, the increase amounts to one- 

 third of the quantity exhaled during rest ; and it lasts for more than an hour 

 afterwards, being manifested in the greater quantity of air respired, and in the 

 larger -percentage of carbonic acid contained in it. If the exercise be prolonged, 

 however, so as to occasion fatigue, it is succeeded by a diminished exhalation. 

 The connection between muscular exertion and the exhalation of carbonic 

 acid, is most remarkably shown in Insects ; in which animals we may witness the 

 rapid transition between the opposite conditions of extreme muscular exertion, 

 and tranquil repose ; and in which the effects of these upon the respiratory pro- 

 cess are not masked by that exhalation of carbonic acid, which is required in 

 warm-blooded animals simply for the maintenance of a fixed temperature. Thus 

 a Humble-Bee was found by Mr. Newport 3 to produce one-third of a cubic inch 

 of carbonic acid, in the course of a single hour, during which its whole body was 

 in a state of constant movement, from the excitement resulting from its capture ; 

 and yet, during the whole twenty-four hours of the succeeding day, which it 

 passed in a state of comparative rest, the quantity of carbonic acid generated 

 by it was absolutely less. 



g. Sleep or watchfulness. The amount of carbonic acid exhaled during sleep 

 is considerably less than that set free in the waking state. This is particularly 

 shown by the experiments of Scharling ; 4 who confined the subjects of them 

 in an air-tight chamber, within which they could sleep, take their meals, &c. 

 Thus in one case, the hourly exhalation sank from 160 to 100, in another from 

 194.7 to 122.3, and in another from 99 to 75.1. The cause of this result is 

 partly to be sought in the cessation of all muscular exertion (save that concerned 

 in the maintenance of the respiration) ; and partly in the diminution in the dis- 

 sipation of the heat of the body itself. 



h. State of the Digestive Process. It is well established, that the exhalation 

 of carbonic acid is greatly increased by eating, and that it is diminished by 

 fasting. Thus Prof. Scharling states the hourly exhalation to have increased 

 in one instance from 145 to 190, after breakfast and a walk j in another from 

 140 to 177, after breakfast alone ; and in another from 111.9 to 188.9, after 

 dinner. The observations of Vierordt are to the same effect. It is remarkable 

 that Alcoholic drinks have a tendency to diminish the exhalation of carbonic 

 acid, especially when taken into an empty stomach ; and it appears from the 

 experiments of Dr. Prout, 5 which have been confirmed as to many points by 

 those of Vierordt, that this diminution continues so long as the alcohol remains 

 unconsumed in the system, and is then followed by a marked increase in the 

 percentage of carbonic acid in the inspired air ; showing that the presence of 

 alcohol tends to prevent the normal oxidation and elimination of the excrementi- 



R6cherches de Physiologie et de Chimie Patliologique," 18-11. 



De Quantitate relativa et absoluta Acidi Carbonic! ab Homine Sano et JEgroto 



exhalati," 1845. 



Phil os. Transact.," 1836. 



Ann. der Chem. und Pharm.," 1843 ; transl. in " Ann. de Claim, et de Plays.," 1843. 



Thomson's Annals of Philosophy," vols. ii. and iv. 



