AND OTHEE PHENOMENA OE EESPIEATION. 
685 
I. QUANTITY OE CAEBONIC ACID EVOLVED, AND CHANGES IN EESPIEATION, WITH 
AND WITHOUT EXEETION, AND WITH AND WITHOUT EOOD, IN THE TWENTY- 
EOUE HOURS OE THE DAY. 
1. With ordinary food. 
No inquirer has hitherto collected the whole carbonic acid evolved by the lungs in 
any considerable part of the day, neither has any one made serial experiments at each 
of the hours of the day. Numerous observers have made isolated experiments at 
various periods of the day (some have even experimented during the night) ; and a few 
have, on certain days, made inquiries at intervals of about an hour for a large part of 
the day ; and from these experiments, varying in number, duration, and interval, the 
quantity of carbonic acid exhaled by the lungs in the twenty-four hours has been deduced. 
KiVOisiEE and Seguix*, in their memoir of 1789, state that the medium quantity 
exhaled by the latter per day was 2 lbs. 5 oz. and 4 gros, but in the memoir of 1790 they 
reduced it to 1 lb. 1 oz. 7 gros and 4 grs. These quantities represent 10 oz. 4 gros and 
5 oz. 7 gros of carbon. They do not give the particulars of their computation. 
CoATHUPEf computes that he expired 5-45 oz. avoirdupois of carbon daily. 
Valextin and BeuxxeeJ, from inquiries prosecuted on several persons, give 173 grs. 
of carbon as the quantity excreted per hour. 
Axdeal and Gavaeeet^, and Schaeling||, from similar inquiries made on a number 
of persons respectively, state that the quantity of carbon burnt per hour varies from 
77-2 grs. to 217-7 grs., and from 80-2 grs. to 154-3 grs., —quantities equal to 283 grs. and 
798 grs., and again to 294 grs. and 666 grs. of carbonic acid per hour. 
ViEEOEDT has made a larger number of experiments, and of a more uniform and serial 
kind than any hitherto published. He found that the medium of five of the highest 
and five of the lowest experiments gave 7-5 grs. of carbonic acid per minute. The minima 
were to the maxima as 1 to 2-25. 
Baeeal^ infen-ed the quantity of carbon burnt by determining the difierence between 
the quantity contained in the aliment and that found in the excretions. It varied in 
himself from 8^ oz. to 12 oz. daily at difierent seasons of the year. 
Baron Liebig**, by a similar mode of inquiry upon a large number of Hessian soldiers, 
found the medium quantity to be 13-9 oz. daily. 
I do not think that we are justified in deducing the total quantity of carbon expired 
in the twenty-four hours from the small quantities determined per minute or per hour 
as above mentioned, when the authors have declined to do so; for most of the experi- 
ments were not intended to embrace all the variations of that period. Andeal and 
Gavaeeet expressly state that they do not feel warranted in doing so from their expe- 
riments. Moreover, no just comparison of the results can be made, since they were 
obtained under dissimilar and also under unrecorded circumstances; and some of them 
include the carbon exhaled by the skin also. The following comparison is therefore only 
to a certain extent true : — 
* Memoires de I’Academie des Sciences. f Loc. cit. J Lehrbucli der Physiologie. 
§ Loc. cit. II Loc. cit. Annales de Chimie, 3 ser. vol. xxv. ** Letters on Chemistry. 
