110 METABOLISM AND GROWTH FROM BIRTH TO PUBERTY. 



borne in mind that food is almost always taken just prior to a test 

 with children under 2 years of age and that 4 or 5 hours may elapse 

 between the taking of food and the beginning of the metabolism meas- 

 urements for the older children. 



On examining the estimates for relative activity in the last column 

 of table 25, one finds that the observations rarely show days when no 

 periods with an activity of either I or II are available. In only two 

 instances (November 15, 1917, and January 18, 1918) does the factor 

 of persistent restlessness appear. The data for these two days are 

 included in the table, however, to give a complete record of the obser- 

 vations with this child. Furthermore, the values for the carbon- 

 dioxide production and the pulse-rate for these active periods are not 

 without interest. 



Almost invariably the high activities (IV, and particularly V and VI) 

 are accompanied by a very great increase in the metabolism and like- 

 wise an increase in the pulse-rate. The periods with activities V 

 and VI usually correspond to the maximum heat production. But 

 absolute reliance must not be placed upon these estimates of activity 

 from the kymograph records, for not infrequently anomalous figures 

 appear. Thus, on November 22, 1916, the last period has an activity 

 of VI, with a total metabolism of 575 calories, which is exceeded by 

 the first two periods of the day, and yet activities II and III are re- 

 corded for these periods. As a rule, however, the metabolism is 

 approximately proportional to the activity, and this factor is a valu- 

 able index of the metabolism of a subject. The pulse-rate is a like 

 valuable index, but taken by itself it is at times, especially with youth, 

 very unreliable. The carbon-dioxide production, the pulse-rate, and 

 relative activity taken together make the selection of minimum 

 periods rarely a matter of great difficulty. When these are confirmed 

 by sustaining figures on days immediately preceding or following, the 

 base-line becomes even more definitely fixed. 



Occasionally low and seemingly aberrant figures appear in table 25, 

 Thus, in the first experimental period on March 15, 1917, but 7.68 

 grams of carbon dioxide were measured, an amount corresponding to 

 but 44 calories per kilogram of body-weight. This value is con- 

 siderably lower than those found for the next three or four days of 

 observation; yet on April 20, 1917, a heat production of 46 calories 

 per kilogram is noted, and it is probable that 7.68 grams of carbon 

 dioxide or 44 calories per kilogram of body-weight represents the 

 true minimum value for March 15. 



While the observations with the child No. 145 were, with one 

 exception, larger in number than those with any of the other children, 

 they are given here in detail primarily to indicate the method of study 

 and analysis of the results. Since we are dealing with an organism 

 that is continually increasing in age, length, and weight, a comparison 



