34 



GASEOUS METABOLISM OF INFANTS. 



second, the graphic records of the muscular activity or muscular repose 

 and the pulse-rate. The main object of the apparatus and its acces- 

 sories is, therefore, to give an accurate measurement on small animals or 

 infants of the carbon dioxide produced and the oxygen consumed, and 

 an interpret able record of the degree of muscular activity or repose, 

 accompanied by pulse observations. 



The carbon dioxide produced by the animal is completely absorbed, 

 the amount excreted being determined by the increase in weight of the 

 absorbing vessels. Gas analyses, with their attendant difficulties of 

 technique, are therefore unnecessary. 



3 I 



rcspiration 



Chamber 



CO 2 produced 

 Op consumed 



Oxygen 

 Introduced 



:.) 



;v 



Pump 



CarbonDioxide 

 Absorbed 



Water 

 Absorbed 



^ 



"a. 



°? deficient 



■?. 



2 deficient 



C0 2 N ? 



°i deficient 



J 



Fig. 1. Schematic outline of respiration apparatus. 



The oxygen is determined directly by noting the amount it is neces- 

 sary to introduce into the respiration chamber in order to secure the 

 same volume of air in the chamber at the beginning and end of the 

 experiment, making due allowance for changes in temperature, pressure, 

 and water-vapor. While usually the amount of oxygen used is deter- 

 mined by allowing oxygen to flow into the respiration chamber from a 

 previously weighed cylinder of the highly compressed gas and noting 

 the loss in weight, it may likewise be accurately determined by passing 

 the gas from a compressed cylinder through a carefully calibrated gas- 

 meter which is submerged in water to prevent gross temperature fluctu- 

 ations. The general plan of the apparatus is shown in the schematic 

 outline given in figure 1. 



As the infant gives off carbon dioxide and consumes oxygen, the air 

 leaving the chamber is rich in carbon dioxide and water-vapor from 

 the lungs and skin of the infant, contains a normal amount of nitrogen, 



