IG 
DR. W. MAECET ON A CHEMICAL INQUIRY INTO 
to be 0’744. I have subjected hunian respiration to experiments of a similar 
description, and obtained results approximating very much to those arrived at bv 
PtEGNAULT and Eeiset, but the inquiry was beset with difficulties, and the figures 
obtained for occluded air do not agree close enough to justify their being quoted on 
this occasion. We may so far accept an occlusion of from 1‘8 to 2 per cent, of 
the air inspired; therefore, the volumes of air expired, as given in this paper, 
increased by that proportion, will yield very nearly the corresponding volumes of 
air inspired. Since, however, the air expired has only been taken into account in 
the present inquiry, the results may safely be accepted as correct relatively to each 
other without introducing any correction. 
The calculations these experiments necessitated were simple, though somewhat 
laborious, until I had completed with the aid of Mr. Townsend a table for reduction 
of volumes, which was found of the greatest use. As I am not aware of such a table 
of figures being in existence, and as it may be useful to others, it is included in the 
present communication. 
The horizontal headings are Barometer readings from 740 to 780 mm., and the 
vertical headings are the temperatures from 10° C. to 25° C. inclusive. The reduction 
of one litre (1000 c.c.) to 0° C. and 760 mm. is given for every Barometer reading 
from 740 to 780 mm., and every temperature from 10° C. to 25° C. 
The correction for fractions of millimetres is additive and obtained by multiplying 
the fraction by the constant 1'2 c.c., or perhaps more correctly 1'25 c.c. The correction 
I’or fractions of degrees Centigrade is suhtractive, and obtained by multiplying the 
fraction by the constant 4'8. The table was made with the usual formula, 
_ VCp -/) _ 
~ 760 (1 + ut) ’ 
Every second or third column of reductions was calculated from the formula, and 
the intervening ones were calculated with constants. The figures obtained by the use 
of constants were tested in a number of cases by calculation from the formula and 
found to be correct within OT per cent. With the assistance of these tables the 
calculation of a ^vhole analysis could be made easily within a quarter of an hour, in 
some cases ten minutes were found sufficient for the purpose. 
The carbonic acid in tlie laboratory air was taken into account, though not deter¬ 
mined in direct connection with the present experiments. A number of analyses of 
this air made on previous occasions showing that the mean COo present could be taken 
in clear weather at 5 parts in 10,000, and in dull weather at 7 parts in 10,000, the 
carbonic acid expired from the lungs was in every case corrected according to these 
data. 
