144 GASEOUS METABOLISM OF INFANTS. 



Furthermore, the data are sufficiently extensive for each subject, 

 as an examination of the table will show that, in all but two instances, 

 at least two periods are used for securing the average value for each 

 infant; in other words, the values were determined in duplicate. In 

 many cases the number of periods for comparison greatly exceeded 

 this ; for example, in one instance 22 periods were available for averaging. 

 The values for two infants, A. S. and H. T., are each based upon only 

 one period and unfortunately these two are among the relatively few 

 infants not under weight. We believe, however, that the probable 

 accuracy of these periods is supplemented by a careful examination of 

 other periods with these infants in which the metabolism accompanying 

 the varying degrees of restlessness and activity was measured. Under 

 the circumstances we do not feel justified in excluding these values from 

 the table, although it is to be noted that in all of the subsequent dis- 

 cussion they may readily be omitted without in any way affecting the 

 general inferences drawn from the research. 



Obviously no infant lives on a minimum metabolic plane throughout 

 the entire 24 hours; indeed, but a small proportion of the total number 

 of the experimental periods could be utilized for this important com- 

 parative study. Nevertheless, since in but two instances was it neces- 

 sary for us to rely upon the computation of the minimum metabolism 

 of the infant from one experimental period, and in only one other 

 instance were our data limited to those secured in two periods on one 

 day, we believe that we have obtained a reasonably accurate estimate 

 of the minimum metabolism of each infant, which justifies critical study 

 and comparison. 



Minimum Extraneous Muscular Activity. 



In the previous discussion of basal metabolism, 1 we pointed out that 

 this term is applied to the minimum metabolism of an infant, unaffected 

 by extraneous muscular activity, and that it is probably best secured 

 a number of hours after the last meal, when the infant is lying perfectly 

 quiet, preferably asleep. It should here be emphasized that the dis- 

 cussion of table 31 and the charts in figures 53 to 65 are based upon 

 this minimum basal metabolism. 



As the investigation progressed, however, and the intimate relation- 

 ship between pulse and muscular activity 2 became apparent, we found 

 ourselves compelled to utilize the pulse records intelligently as an 

 important adjunct in determining the minimum metabolism. Any 

 effort to quantify the kymograph curves which were other than straight 

 lines was obviously very difficult, for a break in the straight line caused 

 by a variation of the pointer over 11 mm. might signify one gross 

 movement, while a number of very small breaks with a sum of 20 or 

 30 mm. need have no such definite mathematical relationship to the 

 heat-production. On the other hand, when the pulse-rate was per- 



'See p. 30. 2 See p. 118. 



