APPARATUS AND EXPERIMENTAL TECHNIQUE. 



The observations with young children ranging in age from a few 

 minutes after birth to puberty included records of the height, body- 

 weight (nude), pulse-rate, body temperature (rectal), muscular 

 activity or repose, and measurements of the gaseous metabolism. 

 From the latter, computations were made of the respiratory quotient. 

 A general record was also kept of the condition of the child during 

 the observations, including such data as drowsiness, sleep, crying, etc. 

 Measurements were likewise made of the body-surface of a consider- 

 able number of the children. 



RESPIRATION APPARATUS. 



The apparatus used for measuring the gaseous metabolism in the 

 studies at the Massachusetts General Hospital has already been fully 

 described in previous publications. 1 In this apparatus a small metal 

 chamber, with a quickly removable cover made air-tight by a water- 

 seal, is connected with a closed-circuit ventilating apparatus. A rotary 

 pump in the ventilating circuit draws the air from the chamber, and 

 forces it through absorbing vessels in which are absorbed the water 

 and carbon dioxide given off by the subject. The air is then returned 

 to the chamber after pure oxygen is introduced from a cylinder of the 

 compressed gas to replace that used by the child. A spirometer in 

 the ventilating circuit provides for expansion in the volume of air. 

 The amount of carbon dioxide expired is measured by weighing the 

 absorbing vessels; the amount of oxygen used is determined by 

 metering the gas introduced into the ventilating circuit. Inside the 

 metal chamber is a wire crib, with mattress, in which the child lies 

 during the period of observation. 



Since only the basal or minimum metabolism was desired in these 

 studies, it was necessary to have a record of the degree of muscular 

 repose or activity of the child to be assured of comparable conditions. 

 While ocular observations of the general condition and activities of the 

 child can be made through the glass window in the cover, such obser- 

 vations give no exact records to be used as a standard in comparisons 

 of the metabolism measurements. The only method of obtaining 

 reliable evidence of the presence or absence of muscular movement is 

 by means of graphic records. Provision is made for such records in 

 this apparatus by suspending one end of the wire crib by a spiral 

 spring, with a small pneumograph parallel to it. By this means the 



1 Benedict and Talbot, Carnegie Inst. Wash. Pub. No. 201, 1914, p. 32; Am. Journ. Diseases of 

 Children, 1914, 8, p. 21. 



28 



