624 
ME. J. BEOUGHTON ON A CEETAIN EXCEETION OE 
to any previous oxidation, since the very latest exposure to oxygen has ceased to be per- 
ceptible. The total daily amount of excreted carbonic acid is hence not comminuent 
with that which is the effect of the single day’s exposure, as would be the case if the 
carbonic acid had no source but that of previous oxidation. It therefore is evident that 
some of the carbonic acid has another source. 
Again, if the peculiar exhalation of carbonic acid, which I have in the foregoing pages 
endeavoured to investigate, were exclusively due to previous oxidation, it is obvious that 
the amount in column “ Air ” for any day should not exceed the sum of the numbers in 
column “ A ” for that and all subsequent days ; but it does exceed this sum in all cases. 
This consideration corroborates the conclusion that there is another source of carbonic 
acid. 
There is an objection to this reasoning which can be made with some justice. “ How 
can we be certain,” it may be urged, “ that the result of a single day’s exposure to an 
oxidizing atmosphere is proportionally the same as that of several consecutive days, or 
as in nature, where the exposure is of course continual ? Perhaps in this case a greater 
proportional effect may take place, and thus the whole amount of carbonic acid may 
be accounted for.” 
This doubt, however, admits of an experimental resolution. If it be true that longer 
exposure causes proportionally larger amounts of carbonic acid to be subsequently 
evolved, then, in a differential experiment like the foregoing, if the time of exposure to 
air be doubled, will the sum of the differences approach nearer to the actual amount 
exhaled on any particular day \ 
To determine this point, an experiment resembling the preceding was made, with the 
difference that the box-leaves were respectively exposed to air and nitrogen for forty- 
eight hours instead of twenty-four. The results of the subsequent determinations were 
as follows : — 
Leaves of Box. 
I. 
Air. 
N. 
A. 
3 
6-40 
4-95 
1-45 
4 
6-96 
5-05 
1*91 
5 
4-88 
4-55 
0-33 
6 
3-26 
2-88 
0-38 
7 
2-65 
2-33 
0-32 
8 
1-52 
1*15 
0*37 
9 
1-45 
1*15 
0-30 
10 
0-86 
0*84 
0-02 
11 
0-76 
0-76 
0-00 
12 
0-45 
0-45 
0-00 
13 
0-45 
0-45 
0-00 
An examination of the foregoing Table shows that the sum of the nth, n+ 1th, 
n+ 2th, &c. differences approaches less near the nth term in column “ Air ” than in the 
former experiment, where the exposure was but for twenty-four hours. This, however, is 
only true in the mean. Calculating from the first seven terms of both Tables, the sum 
