Enquiry into the Heat given out by the Human Body. 247 



six experiments was only by 1'76 per cent. The mean difference (from 

 total figures) from the two persons in eleven experiments amounted 

 to O75 per cent., showing that practically the mean heat emitted was 

 the same in each of two consecutive half-hours. There were, how- 

 ever, differences, though usually slight, in each pair of experiments 

 sometimes an increase, sometimes a decrease the reason of which 

 is difficult to assign. 



The calories given out by the various persons experimented upon 

 were taken generally between lunch and dinner, say at a mean time 

 of about two hoars after a full luncheon, and therefore under the 

 immediate influence of food. But towards the end of the inquiry a 

 certain number of experiments were made just before lunch, corre- 

 sponding with others made after lunch, in order to determine in a 

 general way the effect of a full mid-day meal on the heat-producing 

 power of the body. The mean of seventy-two experiments on four 

 persons, aged respectively 15, 27, 28, and 69, gave 102,907 calories 

 per hour,* and varied from 80,639 to 137,078. In other words, the 

 mean heat given out in one hoar was such as would raise 102,907 

 grams of water by 1 centigrade (from to 1). 



The next point we submitted to enquiry was the relation, if any, 

 between the oxygen absorbed from the air breathed, and the calories 

 emitted at the same time. 



The oxygen absorbed was determined by collecting the air expired 

 by the person in the calorimeter, and estimating the C0 2 and con- 

 tained in the expired air. This was done by methods fully described 

 in previous papers (by W. M.), and need not be further insisted 

 upon. We found the method of breathing for collecting the air 

 expired (inspiration through nose and expiration through mouth) 

 quite satisfactory in every way, the subjects for these experiments 

 being all used to this mode of breathing. 



It is important to observe at the outset that, while there were 

 great differences between the calories found for each person, the 

 oxygen absorbed from the air in every individual case did not 

 exhibit such marked variations ; moreover, except in a very general 

 way, the oxygen absorbed failed to vary in proportion with the 

 number of calories emitted. 



* These experiments include the whole number made, most of them under the 

 influence of a full meal, but a few fasting, or before the mid -day meal. Of course 

 they can only be expected to give a general idea of the mean calories emitted by 

 man, as the amount of heat emitted varies with every different person, and under 

 different conditions as to food and many other circumstances. 



YOL. LXIII. T 



