248 Metabolism of Healthy Man. 



in a larger increase in the carbon-dioxide exhalation on account of a transitory 

 withdrawal of carbon dioxide from the lungs; the heat production may also be 

 affected by variations in body-temperature which could not be satisfactorily 

 measured by the method here used, namely, a clinical thermometer in the 

 mouth; and the oxygen absorption as measured in 1-hour periods is likewise 

 open to serious error. On the other hand, the almost uniform increase in all 

 factors in the experiments shows that there was a distinct increase in metabo- 

 lism. We believe, then, that in the metabolism of 1 hour during the process of 

 dressing and undressing there is an increase in the excretion of carbon dioxide 

 amounting to about one-third of the excretion during rest, an increase of the 

 oxygen absorption of about one-third, and an increase in the heat production 

 of about one-fifth. 



Evidence such as this, when sufficiently accumulated, will permit a much 

 more accurate computation of the total energy transformations of man in 24 

 hours. Up to this time we have had no evidence whatever with regard to the 

 energy transformations incidental to removing and putting on clothes. There 

 is no reason why similar experiments should not be made for a large number of 

 other simple body movements which are a part of every one's daily routine. 

 Such experiments will be made as time permits and opportunity offers. 



PULSE-RATE AS INDEX OF BODY ACTIVITY AND METABOLISM. 



In any attempt to show quantitatively the variations in metabolism accord- 

 ing to different degrees of muscular activity, difficulties are encountered. 

 Designating the different degrees of. activity as consisting of light, moderate, 

 severe, and very severe muscular work does not convey an adequate impression 

 of the muscular activity that actually may be involved in an experiment. In 

 the pulse-rate we have a more accurate method of estimating the activity of 

 normal individuals, and the metabolism that should accompany it. In the 

 course of experiments it has been observed that with very slight activity the 

 pulse and the metabolism are at a minimum. When the activity is increased, 

 the pulse rate is likewise accelerated and there is an increase in the total metab- 

 olism. It has furthermore seemed clear that the increase in the pulse-rate is 

 relatively proportional to the increase in the actual muscular activity observed. 

 Of general interest in this connection is the practical application of these 

 general principles by von Liitzow ' who estimates the capacity of horses for 

 work by noting the lapse of time required for the pulse-rate to become normal 

 after a period of work. 



In an earlier investigation on the influence of inanition on metabolism, it 

 was pointed out that the pulse-rate as determined by the subject from day to 

 day during a 7-day fast varied with the total metabolism. 2 It was there shown 

 that the pulse-rates as thus determined had not the highest scientific value, 



1 K. L. von Liitzow, Deut. Landw. Presse, 1909, 36, p. 245. 



2 Benedict, Carnegie Institution of Washington Publication No. 77, 1907, p. 508. 



