Variations in Metabolism. 245 



For practical purposes, and that is the chief object of the investigation here 

 reported, we may consider that the metabolism when standing is about 15 per 

 cent greater than that when sitting. 



increase in metabolism due to opening and closing food aperture. 



To remove food and dishes from the food aperture and to place therein the 

 vessels containing urine and feces requires a simple series of movements on the 

 part of the subject that must be made several times during the day. Inasmuch 

 as this is the most complicated series of muscular movements involved in a 

 sojourn inside the respiration chamber aside from the work of taking down and 

 putting up the bed, a series of experiments was made to study the increased 

 heat output that results from the operation of opening the food aperture. In 

 this operation as usually carried out the subject rises from an arm-chair, takes 

 one or at the most two steps to the food aperture, unscrews with the right hand 

 the clamp which holds the door, opens it, takes out the material, closes the 

 door, screws down the clamp, and returns to the arm-chair. The experiments 

 in which the increased metabolism was studied were so planned as to have 

 this series of movements carried out with great regularity 12 times each hour 

 and there was activity beyond that just outlined in that the subject opened 

 and closed the food aperture twice during the series of movements. During 

 a preliminary period of 1 to 2 hours before each experiment the subject sat 

 quietly in the chair till the apparatus Avas brought into equilibrium and then 

 began the series of movements. After the beginning of the first period he arose 

 every 5 minutes and went through the operation of opening and closing the 

 food aperture, and carried out the series of movements with great regularity 

 throughout the experiment. The time required by the different subjects for 

 this operation varied somewhat, A. II. M. requiring 19 seconds, A. L. L. 29 

 seconds, and H. E. D. 26 seconds. The subjects were in each case without food 

 since the preceding day. For comparison with these experiments, other experi- 

 ments of different date with the same subjects have been used. In the latter 

 experiments no food was eaten since the preceding day and the subjects sat 

 quietly during the entire period of 8 hours. The results for the metabolism 

 during rest and during the food aperture experiments are given in table 103. 



There is a distinct increase in the metabolism during the active period as 

 indicated by the carbon-dioxide exhalation, oxygen absorption, and heat pro- 

 duction. The water vaporized varied somewhat, as has been pointed out pre- 

 viously. In the last column of the table all the increases are divided by 12, 

 thus giving the amount of carbon dioxide exhaled, the oxygen absorbed, and the 

 heat production in one series of movements. It can be seen that on the aver- 

 age for every time that the food aperture was opened there was an increase in 

 the carbon-dioxide production of 0.42 gram, of oxygen absorption 0.57 gram, 

 and of heat production 1.22 calories. 



These subjects showed that when sitting at rest, fasting, they gave off 23.3 

 grams per hour of carbon dioxide, or about 0.4 gram of carbon dioxide per 



