Enquiry into the Heat given out by the Human Body. 243 



hook soldered to the tube delivering the ice water, for which receiver 

 a flask of a capacity of over a litre was substituted on starting the 

 experiment in the chamber. 



When all was ready, the person under experiment stepped into 

 the calorimeter and sat down on a wooden chair. Immediately 

 afterwards the ice holder was hung up in the chamber to a strong 

 hook fastened to the roof ; then the tube from the upper agitator 

 was connected with the ice holder, and the flask with a thermometer 

 in it, previously weighed, was substituted for the temporary small 

 receiver of the melted ice. At that very instant the stop-watch was 

 started to register the time spent in the chamber, the door was 

 closed and screwed down, and the two agitators were set in motion. 

 It might here be observed that the person in the calorimeter felt no 

 draught, as the air from the lower agitator was driven up behind him 

 through a rose-jet, and that from the upper agitator fell in front of 

 him on its exit from the ice holder. Indeed no sensation of cold was 

 experienced, or any discomfort whatever, the temperature in the 

 chamber remaining exactly the same within a few tenths of a degree 

 centigrade throughout the experiment. In those cases where the 

 air expired had to be collected for analysis, this was done by means 

 of a face-piece strapped to a cap fitting the back of the head. The 

 face-piece was supplied with a glass tube, which was taken between 

 the lips and used for the expiration, while another tube served for 

 the nasal inspiration from the outside of the chamber, without the 

 intervention of any valves. Fresh air was thus inspired through 

 the nose and expired through the mouth a method of breathing 

 with which we were familiar. The inspiratory tube communicated 

 with the external air through the walls of the chambers, while the 

 expiratory tube was connected at will either with the bell-jars or the 

 open air. The bell-jars were suspended in such a way that the 

 person in the chamber never knew when he was breathing into the 

 open air or into the air holders. Three bell-jars were in use, and in 

 many cases an india-rubber bag, faced with oil-silk, was pressed into 

 service, so as to allow of the collection of an increased volume of ex- 

 pired air. The volume of air collected, though only including the air 

 expired during from twenty minutes to half an hour, taken at intervals 

 through the whole time, certainly gives an accurate estimation of 

 the composition of all the air breathed while in the calorimeter, 

 considering that the person remains in a perfect state of repose 

 during that time, except, perhaps, for a minute on entering the 

 chamber. 



On one occasion the whole of the air expired in one hour was 

 collected, and in that experiment it was found that the volume 

 of air expired in half an hour, taken at different intervals of time, 

 was proportional to the volume expired in the whole hour. 



