DISCUSSION OF RESULTS. 145 



sistently low, even periods with kymograph records which were not 

 obviously straight lines could logically be used. So extraordinarily 

 sensitive was the tambour and suspended crib system that the slight 

 fluctuation which would be characterized, for example, as activity II, 

 if unaccompanied by an increase in the pulse-rate, showed almost 

 invariably no effect upon the metabolism. In a relatively few instances 

 a kymograph curve that might be classified as III or between II and 

 III was likewise unaccompanied by an increase in the pulse-rate and 

 corresponded to a low metabolism period. While in general, therefore, 

 the results are drawn from periods of absolute repose as indicated by 

 the kymograph records, we have felt perfectly justified in including 

 periods with activity II and rarely III, if they were accompanied by 

 low minimum pulse-rates and a low metabolism. Such a selection 

 was especially fitting, inasmuch as the average minimum metabolism 

 of each infant was sought and the data are nearly always drawn not 

 from a single isolated period, but from many periods, usually obtained 

 on a number of days. 



Occasionally an extraordinarily low value for the heat-production 

 as computed indirectly was found for a single period. This low value 

 was never included in the periods averaged for the minimum meta- 

 bolism, as we believed it could be easily traced to an error in weighing 

 the carbon-dioxide absorbers, or to some error in technique pertaining 

 to the individual period. An examination of table 23 will show that 

 these very low values were rare, being found possibly 4 or 5 times 

 during the experimenting of a whole winter. It will be seen, therefore, 

 that care was taken with every infant to secure the minimum value, 

 knowing that ultimately several important comparisons would be made. 

 All the information necessary for the use of investigators in making 

 computations by any other method than those here suggested is given 

 in table 23. 1 The data in this statistical table can be used with con- 

 fidence, although we have not thought it wise to reject arbitrarily the 

 very low values found in isolated periods. We firmly believe, however, 

 that these were due to some discrepancy which unavoidably crept into 

 the technique and a careful inspection of the data will show that they 

 should not be employed in drawing average values. 



Minimum Influence of Food. 



In discussing our results, the criticism can be raised that one of the 

 factors outlined in our definition of basal minimum metabolism was 

 not as strictly observed in this study as could be desired, since the 

 infants were rarely in the post-absorptive state, the observations being 

 made for the most part from 1 to 1 J hours after the ingestion of food. 



It has clearly been shown in experiments on men and animals 

 that the ingestion of a mixed diet results in an increased metabolism. 



^ee p. 84. 



