Katabolism and Heat Production. 503 



what manner this high heat production is associated with fever, 100 the experi- 

 ments do not show, since the pulse rate and respiration rate are not known. 

 For the food experiments with S. A. B. there was no increase in the heat pro- 

 duction in experiment No. 72 over the last day of experiment No. 71. Simi- 

 larly in experiment No. 74, the heat production during the night was even 

 less than during the fasting period of experiment No. 73. Experiment No. 76 

 showed, on the average, a slight increase over the heat production of the last 

 days of experiment No. 75. It is reasonable to suppose, therefore, that any 

 variation in the heat production during the ingestion of food is not prolonged 

 into the night period from 1 to 7 a. m. Unpublished experiments made in 

 this laboratory indicate that the extra heat production following the ingestion 

 of food is in large part dissipated shortly after the food is taken, the normal 

 resting metabolism without food being reached after a few hours. 



With the subject S. A. B. it is apparent that the minimum heat production 

 during inanition is not far from 0.0167 calorie per kilogram of body-weight, 

 or 0.52 calorie per square meter of body surface per minute. 



Relation between relative humidity, water of oxidation of organic hydrogen, 

 and total heat production. The water of oxidation of organic hydrogen 

 includes all the organic hydrogen of the protein, fat, and glycogen katabolized. 

 It is, therefore, roughly speaking, a measure of the total katabolism during 

 the day, and since the total katabolism determines the heat production, there 

 should be more or less constant ratios between these two factors. In table 242 

 are recorded the relative humidity, the water of oxidation of organic hydrogen, 

 and the total heat production. 



The relative humidity and its influence on the water of vaporization has 

 already been discussed (see p. 428). The conditions determining the relative 

 humidity inside this type of respiration chamber present certain features of 

 unusual interest. The ventilating air-current enters the respiration chamber 

 absolutely dry. The body of the subject gives off water continuously to this 

 air, and, depending upon the rate of ventilation and muscular activity and 

 consequent water output of the subject, the relative humidity may vary. In 

 all the experiments the rate of ventilation was practically constant (see p. 429), 

 but the influence of internal and external muscular activity (measured by the 

 total heat production) on the variations in relative humidity is worthy of 

 note. In general, the relative humidity decreases with a diminution in the 

 total heat production and increases with a rise in the heat production, although 

 it may be noted that in experiments with the same subject a marked varia- 

 tion in the relative humidity of the air inside the chamber may occur on 

 different days of the different experiments when the total heat production 



109 The special question of the influence of heat production during fever will be 

 discussed in a later report. 



