Enquiry into the Heat given out by the Human Body. 255 



tested on two successive half-hours is found to be the same when the 

 means of the calories are taken, although in each separate experi- 

 ment the heat emitted may vary to some slight extent. 



2. The heat emitted by the same person varies, and the extent of 

 this variation is wider in some subjects than in others ; thus in 

 W. M.'s case the calories emitted in one hour from twenty-six experi- 

 ments varied from 122,124 to 80,639, or by 33'9 per cent, of the 

 larger figure. In the twenty-one experiments of R. B. F. they varied 

 from 106,839 to 80,985, or by 24'2 per cent. With E. R., in eleven 

 experiments, from 137,078 to 111,754, or by 18'5 per cent. 



3. As a fact irrespective of theory the mean number of calories 

 found from three different persons, under similar circumstances of 

 food, &c., corresponding to 1 gram of oxygen absorbed from the 

 air, was the same, and can be stated in round numbers at 4000. 

 Had more experiments been done fasting, this figure would have 

 shown a slight tendency to fall. 



4. Although the mean calories per individual for 1 gram oxygen 

 absorbed under similar circumstances of food, &c., are the same, still 

 in the experiments taken singly, the number of calories correspond- 

 ing to 1 gram oxygen absorbed, vary, and this in a regular way. 

 The greater the heat given out, the greater the calories produced for 

 1 gram oxygen absorbed, and vice versa. Therefore, either a given 

 amount of oxygen absorbed can produce different quantities of heat, 

 or the oxygen found as absorbed does not represent that to which 

 the heat is due; this second alternative appears the more probable. 



5. The influence of a meal, as ascertained on three different 

 persons, is well marked. Taking the midday meal, when mixed 

 food is eaten, generally with a good appetite, the calories emitted 

 about two hours after lunch show an increase over those given out 

 about three or four hours after breakfast. The excess varies in 

 different persons, and according to the kind and amount of food taken. 



6. The calories emitted per kilo, weight of the body are subject 

 to marked variations in different persons. 



A few experiments were made on the influence of clothing on the 

 heat emitted, but we thought it best to reserve that subject for a 

 future communication. 



