RESPIRATION. 



347 



inches. Spallanzani * observed that snails, 

 after a redundant repast, exhaled considerably 

 more carbonic acid gas than when fasting. 

 Similar observations have been made upon 

 insects by Sorgf and Newport f, upon the 

 Mammalia by Ziminermann , and upon the 

 human species by Scharling [|, Valentin ^f, 

 and Vierordt. The most complete experiments 

 on this point are those of Vierordt, performed 

 on himself, the results of which are contained 

 in the following tables. His dinner lasted 

 from 30 minutes past 12 to 1 o'clock : 



To ascertain that this increase in the quan- 

 tity of carbonic acid evolved from the lungs 

 was really dependent upon digestion, and not 

 upon any other cause, the experiment was 

 repeated at the same period of the day when 

 he had not dined, and had eaten nothing since 

 his breakfast at 7 o'clock, and the following 

 results were obtained : 



* Me'moires sur la Respiration, p. 217 223. 



t Disquisitio Physiologica circa Respirationem In- 

 sectonim et Vermium. 1805. 



I London Phil. Trans, for 1836 and 1837. 



The result of Zimmennnnn's experiments is 

 given on Vierordt 's. authority in Wagner's Hand- 

 worterbuch, band ii. S. 884. 



|| Opvis cit. In Scharling's experiments the total 

 quantity of carbonic acid exhaled from the body 

 (luring a given time -was determined, and they arc, 

 therefore, not liable to the errors of those experi- 

 ments where the percentage only was ascertained. 



^f Opus cit. p. 566. Valentin states that an hour 

 after he had taken a meal of bread and butter, the 

 quantity of carbonic acid given off by the lungs was 

 raised from 616-085 to 627-505 English Troy grains 

 per hour, while after a fast of 16 hours it fell to 

 579-972 grains per hour. 



** Physiologic des Athmens, &c. S. 91 tind 94. 



Notwithstanding, therefore, that Prout 

 failed to observe any decided increase in the 

 quantity of carbonic acid gas thrown off by 

 the lungs during digestion, and that Mr. Coa- 

 thupe maintains from his experiments that the 

 carbonic acid in the expired air increases with 

 increased abstinence from food, and that its 

 maximum quantity is before breakfast and imme- 

 diately before dinner *, we must consider the 

 evidence detailed above perfectly conclusive 

 in proving that the quantity of carbonic acid 

 evolved in respiration is considerably in- 

 creased after a full meal. 



Fasting. In describing the effects of di- 

 gestion upon the quantity of carbonic acid 

 evolved from the lungs, we were led to refer 

 to the manner in which the opposite condition 

 of the body, or that of fasting, operates. That 

 fasting diminishes the quantity of carbonic 

 acid in the expired air is not only proved by 

 the facts already mentioned, but also by the 

 experiments of Scharling upon the human 

 species, of Boussingault upon the turtle dove, 

 and of Marchand upon frogs. The two last 

 experimenters found that in very prolonged 

 fasting the quantity of carbonic acid was 

 greatlv diminished. 



Alcohol. Dr. Prout states that alcohol, 

 and all liquors containing it which he had tried, 

 have the remarkable property of diminishing the 

 quantity of carbonic acid gas in the expired 

 air much more than any thing else he had made 

 the subject of experiment, and its effects were 

 most remarkable when taken on an empty 

 stomach. Vierordt mentions, in confirmation 

 of Prout's observations on this point, that in 

 four experiments, after having taken from one 

 half to a bottle of wine, the percentage of 

 carbonic acid had fallen, a quarter of an hour 

 after this, from 4'5'i to 4.'0], and it continued 

 to exercise this effect from one to two hours.-j- 



The quantities of atmospheric air and carbonic acid 

 are calculated in the original tables in cubic centi- 

 metres. In reducing these to English cubic inches, 

 one cubic centimetre has been considered to be equal 

 to "06102523 of an English cubic inch. 



* London, Edinburgh, and Dublin Philos. Magaz. 

 vol. xiv. p. 409 and 4l3. The number of meals and 

 the times at which they were taken explain the re- 

 sults obtained by Mr. Coathupe. He lunched at 

 1 o'clock p. M., and at 2 p. M. the average percentage 

 of carbonic acid gas was raised from 3'92 to 4-17, 

 and thus so far in accordance with the experiments 

 mentioned above. At 5 j P.M. he took a good dinner, 

 with a pint of wine. Now, as alcohol diminishes 

 the quantity of carbonic acid evolved from the lungs, 

 this might have counteracted the effects of diges- 

 tion for a time. It must also be remembered that 

 Mr. Coathupe ascertained only the percentage, not 

 the absolute quantity of carbonic acid evolved ; and 

 Vierordt ascertained by experiment (Physiologic 

 des Athmens, &c. S. 93) that when he drank wine 

 at dinner the percentage of the carbonic acid in flic 

 expired air was diminished ; and that, though its ab- 

 solute quantity was increased, this was not nearly to 

 the same extent as when no wine was taken. Were. 

 experimenters always to detail minutely the circum- 

 stances under which they performed their experi- 

 ments, it would frequently be found, as in the 

 present case, that results, apparently most discord- 

 ant, are not so in reality. 



f Wagner's Handwortevbuch, band ii. S. 884 ; 

 and Physiol. des Athmens, &c. S. 97. 



