94 PHYSIOLOGY OF THE NEW-BORN INFANT. 



BASAL KATABOLISM. 



Direct measurements of the heat-production are only possible with 

 extremely complicated and expensive calorimetric devices. Thus 

 far no one has successfully completed such measurements with infants 

 save Rowland. 1 As it was impracticable to make direct measure- 

 ments of the heat-output in our study of the metabolism of new-born 

 infants, we were obliged to content ourselves with the indirect method 

 of computing the energy from the carbon-dioxide elimination and 

 the oxygen consumption. Fortunately the interesting research of 

 Rowland has shown that this method of determining the energy out- 

 put gives results of a high degree of accuracy. On the other hand, 

 it is impossible to compare the results obtained with an infant in 

 half-hour or hour periods at different times of the day unless there was 

 like extraneous muscular activity in the periods compared. It is 

 much less possible to compare the results obtained with different infants 

 without an assurance of complete muscular repose during the time 

 of the observations. From the beginning of our research we have laid 

 emphasis upon graphic records of the degree of muscular repose, and we 

 are glad to note that this is now bearing fruit in that practically all 

 experimenters are to-day of one mind regarding the absolute necessity 

 of using periods of minimum activity for comparison. 



Even in so extended a series of observations as is reported here, we 

 were not able with all of the infants to secure periods of absolutely 

 minimum muscular activity. A critical examination of all the kymo- 

 graph records was made independently by two skilled observers and 

 periods of practically minimum activity were selected wherever it was 

 possible. In the selection of these periods, however, actual minimum 

 heat values were sought; a careful inspection was therefore made of 

 the heat-production as computed from the carbon dioxide observed. 

 Minimum values were secured for 94 out of the 105 infants. These 

 results have been averaged and are given in table 12. It was rarely 

 necessary to make use of a minimum value obtained from but one period 

 in the series of observations with an infant. These periods of minimum 

 activity and heat-production may be found with comparative ease by 

 referring to the statistical table (see pages 46 to 79). 



lowland, Proc. Soc. Exp. Biol. and Med., 1911, 8, p. 63; Hoppe-Seyler's Zeitschr. f. Physiol. 

 Chem., 1911, 74, p. 1; Trans. 15th Int. Congress on Hygiene and Demography, Washington, 

 1913, 2, p. 438. 



