346 



RESPIRATION. 



The results obtained by Brunner and Valen- 

 tin, and by Vierordt, appear especially trust- 

 worthy ; and though the number of experiments 

 is too small to enable us to deduce averages with 

 any confidence, yet we may in the meantime 

 consider that, in an adult male of middle age, 

 the average quantity of carbonic acid in the 

 expired air is about 4' 35 per cent.*. The quan- 

 tity of carbonic acid gas in the expired air is 

 not uniform in the same individual, but varies 

 repeatedly, even in the course of the twenty- 

 four hours, and these variations are deter- 

 mined by certain conditions of the body and 

 of the surrounding media. 



Period of the day. Dr. Prout believed that 

 he had discovered that the quantity of car- 

 bonic acid formed during respiration is always 

 greater at one and the same period of the day 

 than at any other ; that this maximum occurs 

 between 10 A.M. and 2 P.M., or generally be- 

 tween 11 A. M. and 1 P. M. ; and that the 

 minimum commences about 8 h 30' P. M., and 

 continues nearly uniform till about 3 h 30' 

 A. M. The beginning and end of the period 

 of minimum evolution of carbonic acid he 

 believed to be connected with the beginning 

 and end of twilight, and he adduces some 

 experiments in favour of this opinion. In 

 these experiments Prout attended only to the 

 percentage of the carbonic acid in the expired 

 air, and took no means to ascertain the volume 

 of^air passing through the lungs at the time, 

 an omission which seriously diminishes their 

 value.-]- Prout's results do not accord with 

 the previous experiments of Brande f , nor 



ments were 124 in number, and performed upon 

 himself at almost every hour of the day between 

 8 A. M. and midnight. The difference between the 

 maximum and minimum percentage is great in 

 Coathupe's experiments ; but this was only found in 

 single cases. 



Opus cit. p. 546. These experiments were 34 

 in number, and performed upon three adult males 

 between 33 and 53 years of age. 



|| Article Respiration in Wagner's Handworter- 

 buch, p. 853. Vierordt's experiments were performed 

 upon himself, were nearly 600 in number, were con- 

 tinued over a period of nearly 15 months, and were 

 chiefly made between 9 A. M. and 7 p. M. Vierordt, 

 in his Physiologic des Athmens, has given in a 

 tabular form the results obtained in 578 experi- 

 ments, p. 2165. 



f Animal Chemistry, p. 614. 1843. These expe- 

 riments were made on 10 males and 2 females, and 

 between 11 and 12 o'clock A. M. 



* Dalton (Opus cit. p. 25), Dumas (Essai de 

 Statique Chimique des Etres Organises, 3me edit., 

 p. 87. 1844), and Gay Lussac (Annales de Chimie 

 et de Physique, torn. xi. p. 14. 1844), estimate the 

 average carbonic acid in the expired air at 4 per 

 cent. Apjohn (Dublin Hospital Reports, vol. v. 

 1830), and Macgregor (Transactions of British Sci- 

 entific Association for 1840, p. 87), estimate it at 

 3-6 and 3*5 per cent. The estimate of Allen and 

 Pepys (Opus cit.), and Dr. Fyfe (Dissert. Chemico- 

 Physiol. Inaug. de Copia Acidi Carbonici e Pulmo- 

 nibus inter respirandum evoluti. Edinburgh, 1814), 

 making the average quantity 8- to 8-5 per cent., is 

 undoubtedly considerably too high ; and they were 

 led into this error by the impediment to the free 

 respiration occasioned by the imperfect apparatus 

 employed. 



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



J Nicholson's Journal, vol. xi. p. 82. 



with the subsequent experiments of Coa- 

 thupe* and Vierordt. -f- It would appear, 

 therefore, that the variations in the quantity 

 of carbonic acid in the course of the day do 

 not occur at uniform periods, independent ot 

 other circumstances, as Prout supposed. It 

 is, however, proved by the experiments of 

 Scharling J upon the human species, by Bous- 

 singault upon the turtle dove, and by Mar- 

 chand || upon frogs, that the absolute amount 

 of carbonic acid exhaled is very considerably 

 less during the night than during the day. 

 Scharling gives in the following table the 

 relative proportion of the carbon exhaled 

 during the day and night in six individuals 

 upon whom he experimented : 



The average proportion is 1 during the 

 night to 1-237 during the day, or, in othei 

 words, nearly a fourth part more carbonic 

 acid gas is evolved during the day than during 

 the night.? How much of the diminished 

 evolution of carbonic acid during the night is 

 dependent upon the languor and drowsiness 

 incident to that period, and how much upon the 

 absence of the sun's rays and other causes, it 

 is at present impossible to determine. It 

 appears that this diminished evolution of car- 

 bonic acid during the night does not require 

 the occurrence of sleep, though no doubt it is 

 increased by sleep. 



Digestion. Seguin and Lavoisier **, in 

 their experiments upon Seguin found that 

 when he was in a state of repose and fasting 

 he vitiated only 1210 cubic inches of oxygen 

 gas in an hour, while, during digestion, this 

 was raised to between 1800 and 1900 cubic 



* Opus cit. 



f Physiologic des Athmens, &c., S. 66. 



| Annalen der Chemie und Pharmacie, band xlv. 

 s. 214. 1843. Translated in Annales de Chimie et 

 de Physique, torn. viii. p. 478. 1843. 



Annales de Chim. et de Phys., torn. xi. p. 445. 

 1844. Boussingault calculates from his experiments 

 that, supposing the entire day to be divided into 12 

 hours of sleep, and 12 hours of waking, the quantity 

 of carbon consumed in respiration by the turtle-dove 

 during the day and night would be as follows : 



Carbon consumed in the day (English 



Troy grains per hour) 3-981 



Carbon consumed in the night (ditto) .. 2*500 



|] Journal fur praktische Chemie, von Erdman 

 und Marchand, band xxxiii. S. 148. 1844. 



? Annalen der Chemie und Pharmacie, band xlv. 

 S. 236. 



** Me'moire de 1'Acade'mie Royale for 1789, p. 574, 

 575. Jurine (Encyclopedic Methodique, Medecine, 

 article Air, torn. i. p. 497. 1787) has also maintained 

 that a greater quantity of air is vitiated during 

 digestion. 



