Energy. 479 



heat given off by the cooling of this material does not represent heat actually 

 produced from katabolism. The discussion which follows deals specifically 

 with heat production and takes into account, therefore, the heat elimination 

 corrected for energy gained or lost because of changes of body- weight and 

 body temperature. The results for the measured heat production are recorded 

 for all experiments without food in table 232, together with the distribution of 

 rates and proportions over the main periods of the day. 



By a comparison of the first column of table 232, which gives the total heat 

 production in 24 hours, with column g of table 231, which gives the total heat 

 elimination, some conception can be had of the variations due to the corrections 

 for changes in body temperature, body-weight, etc. It is surprising how slight 

 is the variation between the different experiments. Thus, the average heat 

 production for all the fasting experiments is 1924 calories, while the heat 

 elimination for the same series is 1931 calories. It might seem that the heat 

 elimination may be taken as the measure of the heat production, and indeed in 

 fasting experiments the correctness of this assumption is fairly well estab- 

 lished, since the corrections for the heat production are more or less compen- 

 sating. When the data for shorter periods are desired, however, it is of 

 extreme importance that the heat production rather than the heat elimination 

 be used. The heat production and heat elimination in experiment No. 59 

 were determined not only for the 24 hours but also for the 3-hour periods (see 

 table 17). The differences between the heat production and heat elimination 

 for 3-hour periods are much more marked than for the day. 



The distribution of the heat production over the 6-hour periods has been 

 computed and given in table 232. The proportion of the total heat in 24 

 hours produced for each period has likewise been calculated and recorded in 

 the table. As is to be expected the greater amount is produced during the 

 day period. This is in harmony with the conception that muscular activity 

 determines in large measure the heat production, for even though these are 

 distinctively rest experiments, the muscular activity is obviously greater in 

 the day time than at night. The fact that in some of the experiments the 

 subjects spent not a little time sleeping during the day would, however, tend 

 to more nearly equalize the heat production of the first 12 hours of the day 

 with the last twelve. Eeference to the detailed records of the body movements 

 will show during which hours the subject was asleep. The results show that 

 the heat during the last period of the night, i. e., from 1 a. m. to 7 a. m. is 

 more nearly uniform on the different days of the fasting experiments than 

 during any other period. However, there is, as a rule, a decrease in heat 

 production during this period of the night as the fast progresses. 



The irregularities in muscular activity in the day time render any comparison 

 of the different experiments, and indeed different days of the same experiment, 

 extremely difficult. It is only by taking into account the total sum of body 



