530 OF RESPIRATION. 



troy. 1 From similar collective observations upon the inmates of the Bridewell 

 at Marienschloss (a prison where labor is enforced), he calculates that each in- 

 dividual exhaled 10.5 oz. of carbon daily in the form of carbonic acid ; while 

 in a prison at G-iessen, whose inmates are deprived of all exercise, the daily 

 average was but 8.5 oz. 3 It has been shown by Prof. Scharling, 3 that the total 

 amount of carbon contained in the daily allowance of food and drink in the 

 Danish Navy, is somewhat less than 10.5 oz. ; and as we shall presently see 

 that from l-10th to l-12th of the carbon ingested passes off through other chan- 

 nels, scarcely more than 9.5 oz. of this amount can be consumed by the respi- 

 ratory process. A very exact estimate, though based on more limited data, has 

 been recently made by M. Barral j who experimented upon himself (set. 29) 

 in winter (A) and in summer (B), upon a boy of 6 years old (c), upon a man 

 of 59 years old (D), and upon an unmarried woman of 32 years (E). The fol- 

 lowing table gives the results which he obtained, from an average of five days, 

 in regard to the disposal of the Carbon of the food ; those which relate to its 

 Hydrogen and Oxygen will be noticed hereafter ( 569). 



Weight of Body. Carbon of Food. Carbon excreted. 



In Fecee. In Urine. By Exhalation. 



A 104.5 Ibs. 5654.1 grs. 236.2 grs. 234.6 grs. 5183.3 grs. 



B 4090.0 " 137.4 " 211.5 " 3741.1 



C 33 " 2382.3 " 149.7 " 67.9 " 2164.7 " 



D 129.1 5123.0 " 210.0 " 327.3 " 4585.7 " 



E 134.6 " 4520.8 " 64.8 " 216.1 " 4239.9 " 



Thus the average amount of carbon daily consumed in pulmonary and cutaneous 

 exhalation by M. Barral himself, was in winter 5183.3 grains, or 10.8 oz. troy ; 

 whilst in summer it was but 3741.1 grains, or 7.8 oz. troy ; this difference is 

 quite conformable to what might have been anticipated from the results of a 

 different mode of experimenting ( 564, a) j and it throws some light on the 

 discrepancies in the results of other measurements, to find that the seasonal 

 variation is scarcely less than one-third of the mean between these two amounts. 

 The other results correspond closely with the statements of MM. Andral and 

 G-avarret, in regard to the higher proportion of carbonic acid exhaled (as com- 

 pared with the bulk of the body) by children ; and the smaller proportion thrown 

 off by men advanced in years, and by women. 



567. It is not only by an oxygenated atmosphere, that the removal of Car- 

 bonic acid from the blood may be effected. For although it was formerly sup- 

 posed that the exhaled carbonic acid is generated in the lungs by the combina- 

 tion of atmospheric oxygen with the carbonaceous matters of the blood, and that 

 the inhalation of oxygen is therefore immediately necessary for its production, 

 yet it is now quite certain that this carbonic acid exists preformed in venous 

 blood, and that the oxygen introduced is carried into the arterial circulation, 

 instead of being at once returned to the air in the state of carbonic acid. That 

 this (which was first advanced by Lagrange and Hassenfratz) is the true view 

 of the case, is proved by experiments of two kinds ; those, namely, which have 

 shown that a larger proportion of oxygen exists in arterial blood, and a larger 

 proportion of carbonic acid in venous blood ( 163) ; and those which demon- 



1 " Animal Chemistry," 3d edit. p. 13. The mode in which this estimate was made, 

 however, was very far from exact ; as it rests on the assumption that the carbon of the 

 feces and urine was no more than equal to that of certain extra articles of diet supposed 

 to have been consumed, and that all the carbon of the regular allowance of bread, meat, 

 and vegetables, must have passed off by the atmosphere. Its great discordance with other 

 results leaves little room for doubt, that, even if not far from being true for the particular 

 case, it cannot be admitted as representing the usual average. 



2 Op. cit,, p. 46. 3 Ann. der Chem. und Pharm.," 1846. 

 4 "Ann. de China, et de Phys.,'' torn. xxv. 



