RESPIRATION. 



351 



In these experiments of Scharling the evo- 

 lution of carbonic acid by the skin was in- 

 cluded, with that evolved through the mouth 

 and nostrils ; and the quantity is calculated 

 for the twenty-four hours. But in some sub- 



relative amount of the loss by these two dif- 

 ferent channels in an hour. In other respects, 

 he has endeavoured to assimilate his experi- 

 ments, in regard to the hour of the day, &c., 

 to those of Andral and Gavarret, and has 



sequent experiments, by uniting the use of given the following comparative view of the 

 the mask used by Andral and Gavarret with results : 

 the box, he has been enabled to ascertain the 



Influence of tf/e respiratory movements 

 upon the evolution of carbonic acid from the 

 lungs. This point has been particularly ex- 

 amined by Vierordt in 171 experiments upon 

 himself, and he has ascertained that the fre- 

 quency, extent, and duration of the respiratory 

 movements have a marked effect, not only 

 upon the relative proportion of the carbonic 

 acid gas in the expired air, but also upon the 

 absolute quantity evolved from the lungs in a 

 given time.J We shall afterwards find, when 

 we come to describe the theory of respiration, 

 that the results obtained by Vierordt are of 

 considerable importance in a theoretical point 

 of view. 



Frequency of the respiratory movements. 

 When the number of respirations is less than 

 usual, the percentage of the carbonic acid in 

 the expired air is increased, while its absolute 

 quantity is diminished ; on the other hand, 

 when the respirations are more frequent than 

 usual, the percentage of carbonic acid in the 

 expired air is diminished, while its absolute 

 quantity is increased. Vierordt endeavours 

 to point out that the diminution in the per- 

 centage of the carbonic acid gas in the ex- 



six experiments on themselves, calculate that 172-664 

 Troy grains of carbon were thrown oft' from the 

 lungs in an hour. 



f This table is given in the form into which it 

 has been thrown by Hannover (De Qtiantitate 

 relativa et absoluta Acidi Carbonici ab homine sano 

 et jegroto exhalati, p. 17. 1845) and the kilo- 

 grammes and grammes in the original table have 

 been reduced to Troy pounds and Troy grains. 



* As the boy upon whom Scharling experimented 

 was of slender form, he has taken the average of the 

 results of Andral and Gavarret upon two boys of 

 10 and 8 years as the standard of comparison in 

 this case. 



f Wohler and Liebig's Annalen der Chemie und 

 Pharmacie, band Ivii. S. 1. 1846. The male adult 

 and the boy were naked during the experiment. 



J Physiologic des Athmens, vierter abschnitt, 

 S. 102149. 



pired air when the respirations are more fre- 

 quent, probably bears a certain proportion to 

 their frequency or length per minute, sup- 

 posing their bulk to be the same. The 

 operation of this law, according to Vierordt, 

 may be illustrated as follows. Let us take 

 the average number of respirations in a state 

 of rest as 12, and suppose these to be 

 doubled or increased to 24, the relative 

 percentage of carbonic acid will be dimi- 

 nished by 0'8 ; if the number of respirations 

 be again doubled, or increased to 48, the 

 carbonic acid will suffer a still further dimi- 

 nution of 0'4 per cent. ; and if the respira- 

 tion be again doubled, and increased to 96 

 per minute, the carbonic acid will suffer a 

 farther reduction of 0'2 per cent. On the 

 other hand, if the number of respirations 

 be less than 12 (here taken as the normal 

 number of respirations by Vierordt) by one 

 half or reduced to 6 in the minute, the re- 

 lative percentage of carbonic acid will be in- 

 creased above what it is in the normal fre- 

 quency by 1'6. If the percentage of carbonic 

 acid in the expired air be 4M, when the re- 

 spirations are 12 in the minute, it will be 

 5'7 per cent, when the respirations are 6, 

 and 2'7 per cent, when they are 96 in the 

 minute. Proceeding upon the existence of 

 this law, he supposes that if the respirations 

 were increased from 96 to twice that number, 

 or 192, the percentage of the expired air 

 would suffer a farther reduction of only O'l 

 per cent. ; in other words, it would be reduced 

 from 2'7 to 2'6 per cent. This last ratio, viz. 

 2'6, he believes to be the smallest percentage 

 of carbonic acid gas that the expired air can 

 present. If Vierordt be correct in supposing 

 that the percentage of carbonic acid in the 

 expired air has a fixed arithmetical proportion 

 to the frequency or length of the respiratory 

 movements, we could, after determining the 

 normal number of respirations, the bulk of air 

 expired, and the percentage of carbonic acid 



