EFFECTS OF RESPIRATION ON THE AIR. 



391 



were obtained iu the case of a healthy man, net. 28, weighing 132 Ibs., fed 

 on ordinary diet, engaged in reading and cleaning watches, and extending 

 over twenty-four hours: 



A few days later the same man worked till exhausted. 



The connection between muscular exertion and the exhalation of Car- 

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

 witness the rapid transition between the opposite conditions of extreme mus- 

 cular exertion and tranquil repose; and in which the effects of these upon 

 the respiratory process 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 1 to pro- 

 duce 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 com- 

 parative rest, the quantity of Carbonic acid generated by it was absolutely 

 less. 



vin. Sleep or Watchfulness. The amount of Carbonic acid exhaled during 

 sleep is considerably less than that set free in the waking state. This is par- 

 ticularly shown by the experiments of Scharling; 2 who confined the subjects 

 of them in an air-tight chamber, within which they could sleep, take their 

 meals, etc. 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. With cus- 

 tomary food and exercise Petteukofer and Voit, in one experiment found 

 that of the total amount of Carbonic acid eliminated during 24 hours, 58 

 per cent, was given off during the 12 hours of the day, and 42 per cent dur- 

 ing the 12 hours of the night; whilst 33 per cent, of the oxygen was taken up 

 by day, and 67 by night. Dr. Ed. Smith found that 4.88 and 4.99 grs. of Car- 

 bonic acid were exhaled per minute during light sleep from 1 to 3 A.M., and 

 he estimates the quantity in profound sleep at 4s grs. He also observed 

 that 5.7 grs., 5.94 grs., and 6.1 grs. per minute were evolved at 1.30, 2.30, and 

 6.15 A.M., whilst awake, the average amount during the waking day being 

 9.77 grs. per minute in the same person. The cause of this result is partly 

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



1 Pbilos. Transact., 1836. 



3 Ann. der Chem. und Pharm., 1843; transl. in Ann. de Chim. et de Phys., 1843. 



