METABOLISM DURING CHEWING. 127 



For the respiration experiments the output of heat was computed 

 by the indirect method. These experiments consisted of two series of 

 periods, in the first of which the subject was without food and did no 

 chewing. As the measurements of the metabolism were not con- 

 tinuous, it was necessary to compute the values given in tables 67 

 and 68 for the total increment due to chewing by the best method 

 obtainable and to make certain assumptions. 



Tables 60 to 66 show both the average heat production for the 

 periods without food or chewing, {. e., the basal value for the day, and 

 the heat output for each of the periods with chewing. The increase 

 in the metabolism in the periods with chewing has been obtained by 

 comparing the basal value for the day with the heat computed for 

 each period. These increments of heat represent the results of two 

 to four periods in which the metabolism was measured. The total 

 time of chewing in the several respiration experiments varied from 53 

 minutes to 2 hours 19 minutes; the total duration of the measurement 

 of the metabolism (not continuous) was from 30 to 60 minutes. In 

 computing the total increment in the metabolism due to chewing 

 (see table 68), it was assumed that the increase was coincident with the 

 beginning of chewing. It was furthermore assumed that the rate of 

 increase in the periods between the beginning of chewing and the begin- 

 ning of the measurements (6 to 14 minutes), also in the intervals 

 between the periods of measurement (6 to 40 minutes), was the same 

 as that in the measured periods and that the average increment 

 obtained for these periods represents the rate of increase in the 

 metabolism for the total time of observation i. e., from the beginning 

 of chewing to the end of the last period. The total increment in the 

 metabolism for this time was therefore computed by direct proportion. 



For example, in the experiment with V. G., January 5, 1911 (see 

 table 62, page 133), the average basal value for the heat output per min- 

 ute obtained in periods without food and without the work of chewing, 

 was 1.13 calories. The subject began chewing 10 minutes before the 

 measurements of the metabolism commenced. The values obtained 

 for the respective chewing periods were 1.46, 1.52, 1.43, and 1.32 cal- 

 ories for a total period of measurement of 53 minutes. The average 

 increment in the metabolism during the measured periods of chewing 

 was therefore 0.30 calorie per minute. Using this value and the 

 total time of chewing, that is, the period from ll h ll m a. m. to I h 30 m 

 p. m., or 2 hours 19 minutes, the total increase in the metabolism 

 (139 X 0.30) was computed to be 42 calories. The basal value corre- 

 sponding to this period (139 by 1.13) was 157 calories. The percentage 

 increase in the metabolism (42 -J- 157) was therefore 27 per cent. 



Statistical data not included in the tables or in the discussion are 

 given for all of the experiments in the following paragraphs. The 

 data for pulse rate and respiration rate represent averages of the indi- 



