350 



RESPIRATION. 



acid evolved from the lungs to one hour, 

 being perfectly aware of the fallacy of at- 

 tempting to estimate from experiments so 

 limited as to time, the quantity given off in the 

 twenty-four hours. Scharling conducted his 

 experiments in a different manner. He en- 

 closed the individuals experimented on in a 

 box, perfectly air-tight, and so large as to 

 permit a person to work, read, or even sleep, 

 during the experiment. Tubes were fixed in 

 the box, to admit the external air freely, and 

 to conduct the expired air into an apparatus 

 fitted for determining the amount of the car- 

 bonic acid. The individuals experimented on 

 remained in the box generally for an hour at 

 a time, sometimes an hour and a half, but 

 also often from thirty to forty minutes only ; 

 and precautions were taken to keep up a free 

 circulation of atmospheric air through the 

 box during the whole of the experiment. His 

 experiments were performed upon six persons, 

 of different ages and of both sexes. 



Andral and Gavarret have drawn the fol- 

 lowing conclusions from their experiments: 



1. The quantity of carbonic acid gas ex- 

 haled from the lungs, in a given time, varies 

 according to the age, the sex, and the consti- 

 tution of individuals ; and that, independently 

 of the weight of the body. 2. At all periods 

 of life extending from 8 years (the earliest 

 age subjected to experiments) up to the most 

 advanced old age, the quantity of carbonic 

 acid evolved from the lungs differs in the two 

 sexes, but, cceteris parilnts, the male exhales a 

 considerably larger quantity than the female. 

 This difference is most marked between 16 

 and 40 years of age, during which period the 

 male generally evolves nearly twice as much 

 as the female. 3. In the male, the quantity 

 of carbonic acid exhaled goes on conti- 

 nually increasing from 8 to 30 years of age, 

 and becomes suddenly very great at the age 

 of puberty. After 30 years of age it begins 

 to decrease, and this so much the more de- 

 cidedly as the person approaches extreme old 

 age, at which period it may be reduced to the 

 quantity evolved at 10 years of age. 4. In 

 the female also, the evolution of carbonic acid 

 increases from infancy up to puberty ; but at 

 this period, contrary to what takes place in 

 the mule, it remains stationary, so long as the 

 menstrual secretion continues natural. At 

 the time the menses cease, the evolution of 

 carbonic acid gas from the lungs undergoes a 

 marked augmentation ; but after a while it 

 begins to decrease, as in the male, and pro- 

 portionally as she advances towards old age. 

 5. In the female, during gestation, the exhala- 

 tion of carbonic acid from the lungs equals 

 the quantity exhaled at the period of the ces- 

 sation of the menses. 6. In both sexes, and 

 at all ages, the quantity of carbonic acid is so 

 much the greater, as the constitution is 

 stronger and the muscular force more deve- 

 loped. 



The most important of the data upon 

 which the above inferences are founded are as 

 follows : 



In the male child, in his progress upwards 



from his 8th to his 15th years, the quantity 

 of carbon given off by the lungs was raised, 

 on an average, from 5 grammes (77-165 Troy 

 grains) to 8'7 grammes (134-267 Troy grains) 

 per hour ; while in the female at the same 

 age it was on an average 1 gramme (15-433 

 Troy grains) less per hour. In the male at 

 16 years of age, or soon after puberty, it sud- 

 denly increased to 157'416 Troy grains, on an 

 average, per hour ; and from this period up to 

 the age of 20 and 25 it gradually increased, 

 on an average, to 172'849 and 191-369 Troy 

 grains per hour. At this point it remained 

 nearly stationary until about 40 years of age, 

 when it began to undergo a slight diminution, 

 but not to any great extent until 60 years of 

 age. Adult females, who menstruated regu- 

 larly, lost, on an average, 98'771 grains only 

 of carbon, by the lungs, in an hour, a quan- 

 tity not greater than that lost by girls. Take 

 the average loss of carbon, by the lungs, in 

 the male at 174^392 grains between the ages 

 of 15 and 20 years, it is, on an average, 155'873 

 grains between 40 and 60 years; and 141'953 

 grains between 60 and 80 years. In the fe- 

 male, at the period of the cessation of the 

 menses, the loss of carbon is suddenly ele- 

 vated from an average of 98-77 1 to ] 29*637 

 grains per hour; and a similar elevation, and 

 nearly to the same extent, was observed in 

 four females during pregnancy. In females 

 between 50 and 60 years of age, the loss was 

 1 12-660 grains, and between 60 and 80 it was, 

 on an average, 104'944 grains in an hour. In 

 one female of 82 years, it was 92'595 grains, 

 and in a male of 102, but remarkably hale for 

 his years, it was 91-590 grains. In a male, 

 aged 26, and remarkable for his muscular de- 

 velopment, the loss was as high as 217-105 

 grains, while in another male, aged 45, of mo- 

 derate height, but extremely feeble muscular 

 development, it amounted on an average only 

 to 132'723 grains an hour.* Scharling, after 

 allowing seven hours for sleep to an adult, 

 and nine for a child, calculates, from his 

 experiments on six individuals, the amount 

 of the loss of carbon from the body as 

 follows : 



* Brunner and Valentin (opus cit. p. 567), from 



