AJST) OTHEE PHENOMENA OE EESPIEATION. 
699 
observers, and they have been ascribed to food, exertion, and sleep. Some of these 
obsei^'ers, as Peout and Coathupe, determined only the per-centage in the expired 
ail , an inquiiy of no value in determining the total amount of carbonic acid exhaled. 
Lavoisiee states that the quantity differs every moment, and with every person, but each 
person has a law for himself. Schaeluxg states that the proportion of the night to the 
day varied from as 1 to 1-225 to as 1 to 1*42, whilst Maechaxd regarded the difference 
as inconsiderable and due simply to quietude. In my experiments the variations during 
the day were extremely great, so much so that the maximum and minimum quantities 
of carbonic acid usually differed to the extent of more than half the latter. They were 
as follows in grains per mmute in the four- sets of inquiries : 
Min. Mas. 
Myself 6-25 and 9-69 
8-68 and 11-53 
continuous [7 -81 aud 11 
utqumes. 
Min. Max. 
Mr. Moul 6-76 and 11-56 
6-76 and 9-35 
Min. Max. 
Dr. Murie . . . . 6-14 and 9-25 
Professor Frankland 4-58 and 8-32 
the total being 6-/4 and 10-43 grs. per minute. 
^ These variations were due to food, and were of such a nature that an increase began 
directly after a meal and progressed to a maximum, after which they declined gradually 
to a minimum until the following meal. 
Generally the maximum quantity was observed in from one to two hours after a meal, 
and after each meal, but after the breakfast and tea meals it was the greatest, and both 
were nearly the same. The minima were observed before a meal, and hence there were 
five in each day, viz. before breakfast, dinner, tea, and supper, and some time after 
supper ; and it is very noticeable that they were nearly the same at each of those periods. 
Hence there is in a state of quietude in each day a minimum line below which the 
system does not pass, and also a maximum which it does not exceed, the difference 
between the two bemg due to the temporary influence of food. In several of the 
inquiries, however, as for example in that of Professor Feankland, in my first and 
in IVIi-. Moul’s second experiment, there was not in the afternoon the ordinary amount 
of diminution in the quantity of carbonic acid exhaled ; and as this was exceptional, and 
v\e dined before our usual dinner hour, it was probably oiving to food having been 
supplied before the action upon the respiration of the previous quantity had ceased 
(Plate XXXIII. fig. 1, March 12). There can be no doubt that, with a suitable interval 
between meals, there are striking alternate elevations and depressions in the line repre- 
senting the quantity of carbonic acid excreted. 
A reference to the above maximum and minimum quantities, and to the variations 
hour by hour as shown in the Tables I. II. III. and IV., with the want of uniformity 
any of these quantities, proves that any attempt to determine the whole carbonic 
acid evolved in a day from isolated or irregular observations must be futile. They, 
4 z 2 
