126 FOOD INGESTION AND ENERGY TRANSFORMATIONS. 



when significant. If available, the nitrogen in the urine excreted 

 during the food periods is given, either as an average figure with the 

 food data at the head of the table or for the individual periods in a 

 separate column. 



The tables for the respiration experiments give the data for the diet, 

 also the average basal values per minute for the gaseous exchange, the 

 computed heat production, the respiration rate, and the pulse rate. 

 The time of beginning each period of measurement after food and the 

 results of the observations are shown, with the addition in some cases 

 of the values for the inspiratory ventilation. While the increments in 

 the metabolism have not been calculated, they are readily noted by a 

 comparison of the average basal values with the data recorded for 

 each period following the ingestion of food. The time when the food 

 was taken is given in a footnote. In both the calorimeter and respira- 

 tion experiments the subjects usually ate the food in 15 or 20 minutes; 

 if longer than this was required, the time thus occupied is stated in a 

 footnote. 



METABOLISM DURING CHEWING. 



Of the various processes classified by Professor Armsby 1 as prior to 

 actual digestion, the work of prehension is hardly suitable for experi- 

 mental study, since it would vary greatly with different individuals and 

 with the different kinds of food consumed. On the other hand, mas- 

 tication is a physiological function accompanying all ingestion of food. 

 Indeed, a cult with many adherents has been established to advocate 

 prolonged mastication. Hence information regarding the probable 

 energy transformations as a result of mastication has unusual interest. 

 To study this question, a series of experiments was made in which the 

 subject chewed gum for a considerable length of time. This study was 

 supplemented by a second series of experiments in which a rubber 

 stopper was substituted for the chewing gum. 



STATISTICS OF EXPERIMENTS. 



The calorimeter experiments included 3 experiments with the respira- 

 tion calorimeter at Middletown, Connecticut (tables 52 to 54), 4 with 

 the chair calorimeter (tables 55 and 57 to 59) and 1 with the bed 

 calorimeter in Boston, Massachusetts (table 56). In all of these the 

 subject chewed gum. In addition, 5 respiration experiments were 

 made with the subject chewing gum (tables 60 to 64) and two respira- 

 tion experiments in which a rubber stopper was chewed vigorously 

 (tables 65 and 66). A summary of the values obtained for the heat 

 production in these experiments is included in tables 67 and 68. 



'Armsby, The principles of animal nutrition, 2d ed., 1906, p. 374. 



