eee FET ~~. 
Se I 7 eens 
ON CALORIMETRIC OBSERVATIONS ON MAN. 263 
oxygen. Largely from reasons of economy no attempt has been made 
to copy this procedure and apparatus. In place of the closed circuit of 
tubes through which air is led away from and back to the calori- 
meter we have an open system. By a length of suitably wide tubing 
the air-entrance is carried to a point at some little distance from the 
calorimeter, and therefore some distance from the air disturbed by the 
presence of the observers. A powerful fan driving a large current of air 
across the path of this tube further secures this separation. Similarly 
by a length of tubing the air-exit is carried into another room, in which 
the pump and gas meter are situated. The entrance and exit are thus 
widely separated. 
The tubes carrying the ‘ entering’ and the ‘ leaving’ air have each, 
at a certain point, been subdivided into three separate paths, and suit- 
able arrangements made so that sampling-bottles may be inserted or 
removed from one of these short subdivisions of the air-path. Thus a 
definite fraction of the air-stream traverses each sampling-bottle, and 
is always allowed to traverse it for a time sufficient to ensure the com- 
plete replacement of its original contents by air similar to that traversing 
the remaining fraction of the air-path. 
In twenty of the experiments in which Professor Macdonald has 
collected the data of heat-production I have analysed samples of the 
“leaving air’ obtained in this way. In the earlier cases the ‘ entering 
air’ was also sampled and analysed, but I found its content of carbon- 
dioxide so relatively constant that I abandoned dealing with it for the 
present. In thirteen of these experiments the ‘leaving air’ was dealt 
with as follows :—The sample-bottles were of large size (7 to 8 litres), to 
the large volume of air contained in them baryta solution was added, 
shaken up and allowed to stand, and then titrated with a known strength 
of oxalic acid. In the application of this ‘ Pettenkofer method ’ I owe 
much to the assistance of Mr. W. J. Jarrard, B.Sc. The results 
obtained by this method were consistent in the different experiments, 
and in each experiment provided results giving, when plotted out, 
comparatively smooth curves, which showed the output of carbon- 
dioxide from the calorimeter as gradually increasing towards a level 
reached somewhere before the end of the first hour of cycling and then 
sustained for the second hour. 
In the remaining seven of these experiments I have replaced this 
method by a volumetric method, using the apparatus devised by 
Dr. J. S. Haldane (large laboratory type), substituting smaller sampling 
' vessels of approximately 70 c.c. capacity as now sufficient. Up to the 
present the plotted curves of results obtained by this method have not 
been as smooth as those originally obtained, but this will be improved 
upon when the air-stream has been diminished so as to enable me to 
deal with larger percentage values. The quantity of air traversing the 
system has varied from 300-410 cubic feet per hour, and will next year 
be substantially diminished in the interests of these gas-analyses, and 
peculiarly so because of oxygen determinations, which ‘will then be 
instituted. This desire to deal later with the oxygen values explains 
a preference for the Haldane method. 
Adding to the results of such experimental determinations of the 
