MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



297 



found in the ventilating air current in order to obtain the actual amounl exhaled during the 

 interval. On the other hand when the transition is made from a period of considerable activity 

 to one of rest, there i- a gradual diminution of the quantity of residual carbon dioxid and water 

 in the air of the chamber. This residual carbon dioxid is carried out in the ventilating air 

 current during the period, but was actually given off during some preceding period. The total 

 amount measured must, therefore, be diminished by the difference in the quantities of residual 

 carbon dioxid at the beginning and end of the period. Furthermore, with the increased water 

 content of the air consequent upon increased muscular work, the amount of water accumulated 

 by condensation upon the water system or •'absorbers** may be gradually increased. Indeed, 

 the amount of water thus condensed in periods of active work is apt to be SO large that a portion 

 gradually drips from the troughs or shields beneath the water system into the "drip flasks*" 

 suspended at the end of the shields. This water i> called ••drip."* The weight of the water 

 system or absorbers also increases through the condensation of moisture which does not run off 

 into the drip. On the other hand, with the change from work to rest, the weight of the 

 absorbers diminishes because of evaporation of some of the moisture condensed thereon during 

 the previous period. 



In order to determine the actual amount of carbon dioxid and water vapor in the air of the 

 chamber at the close of each period, samples of the air are drawn and the quantities of carbon 

 dioxid and water determined. At the same time the absorbers are weighed and the drip 

 collected. The data thus obtained, shown in Table X. serve for correcting the amounts of 

 carbon dioxid and water found in the ventilating air current, a- shown in Tables XI and XII 

 beyond. 



In experiment No. 12 drip was not weighed at the end of each period, but was poured intoa 

 bottle and the total amount for each 2± hours passed out at the close of the day and weighed. 

 We have, therefore, no measure of the amount of drip in the different periods. It is altogether 

 improbable that the amount was uniform from period to period, but in lack of any indication as 

 to how it should be subdivided, the amounts have been apportioned equally among the four 

 periods of the day. While this may introduce some error in individual periods, it does not 

 affect the accuracy of the figures for the whole day. 



Table X. — Comparison of residual amounts of carbon dioxid and water in tfie chamber <il tin: beginning and end of each 

 period and thr corresponding gain or loss — Metabolism experiment No. 1 .'. 



