40 PHYSIOLOGY OF THE NEW-BORN INFANT. 



new-born infant, will not cause a marked difference in the character 

 of the katabolism so that when a comparison is made of the carbon- 

 dioxide production and the oxygen consumption for the entire period 

 of observation, i. e., 1% to 2 hours, the result may be fairly considered as 

 representing the average respiratory quotient for that period. If 

 in this time there is a 30-minute period of complete muscular repose 

 during which the carbon-dioxide output has been measured, the heat- 

 output may be computed for this minimum period by the method of 

 indirect calorimetry, i. e., by multiplying the carbon-dioxide production 

 for the 30-minute period by the calorific equivalent of carbon dioxide 

 for the respiratory quotient prevailing during the entire period of 1^ 

 to 2 hours. 



The heat output for the entire period of observation may be obtained 

 not only by using the carbon-dioxide production for that period, but 

 may also be secured by multiplying the oxygen consumption by the 

 calorific equivalent of oxygen for the respiratory quotient during the 

 period of observation. In view of the technical difficulties of meas- 

 uring the oxygen consumption, however, this factor may not properly 

 be used for calculating the heat-output for the minimum period. 1 



It may be argued that the assumption of a representative respiratory 

 quotient for the entire period of observation for use in computing the 

 heat-output during the minimum period may lead to error, since there 

 may be a slight, normal fall in the respiratory quotient (particularly 

 if the observation is preceded by nursing) , this fall being due to the fact 

 that the carbohydrate of milk probably burns more rapidly than the 

 fat and the protein. It is fair to assume, however, that the error caused 

 by the use of this average respiratory quotient in the formula for indi- 

 rectly computing the heat-output from the carbon-dioxide production 

 for a 30-minute period is certainly no greater and is probably less than 

 that involved in the direct measurement of the oxygen consumption 

 with its attendant temperature and barometric measurements at the 

 beginning and end of the period. In our research we desired not only to 

 determine the character of the katabolism, but also, if possible, to deter- 

 mine the minimum basal metabolism. Since this was usually deter- 

 minable only in 30-minute periods, the method of computation just 

 outlined was applied to these experiments. 



l lt should be said that the proper thermometer, barometer, psyclirometer, spirometer, and meter 

 readings were recorded at the end of every period. Calculations based upon these showed for the 

 most part good agreement in each period between the heat indirectly calculated from the carbon- 

 dioxide output and the average respiratory quotient and that calculated from the oxygen consump- 

 tion and the average respiratory quotient. This fact has been cited in discussing the maximum 

 heat-output (see table 18, p. 113). Nevertheless, as each absolute value for the oxygen determina- 

 tion may possibly be subject to the errors previously cited, the values for the heat-output in this 

 publication, except in table 18, have been calculated from the carbon-dioxide determinations, 

 using the calorific value of carbon dioxide corresponding to the average respiratory quotient for 

 the entire sojourn inside the chamber. 



