524 



JOHN R. MURLIN 



amount so indicated by the residual analysis. The quality of the oxygen 

 supplied is likewise controlled by analysis. 



c. Apparatus of Atwater and Benedict (d}. These authors introduced 

 the use of an eccentric blower (Fig. 6) for driving the air through the ab- 

 sorption system and back to the respiration chamber. The original cham- 

 ber described on page 518 for the open-circuit apparatus was adapted 

 to the new type of ventilation shown in Fig. 6. In the upper part of the fig- 

 ure the respiration chamber is shown and below it is the blower and ab- 

 sorbing or purifying system. Air from the chamber containing nitrogen,' 

 carbon dioxid, water vapor and a somewhat diminished percentage of 

 oxygen passes through the blower and enters the absorption system. Here 

 it is forced through sulphuric acid to remove the water vapor and through 

 a specially prepared soda lime which takes out the carbon dioxid; the 



soda lime, however, con- 

 tains water some of which 

 is taken up by the dry 

 air. A second sulphuric 

 acid absorber to catch 

 Vhis water is therefore 

 necessary and the total 

 CO 2 absorption is found 

 by the gain in weight of 

 these two vessels. The 

 air is now freed of car- 

 bon dioxid and water, 

 but is still deficient in 

 oxygen. The latter in 

 requisite amount is ad- 

 mitted from a cylinder of 

 compressed oxygen through an opening in the ventilating pipe (see Fig. 

 6) and the air now restored to its original composition re-enters the respi- 

 ration chamber. 



The respiration chamber of the original construction continued to be 

 used as a calorimeter. In later patterns of this respiration calorimeter 

 which have been constructed at the Nutrition Laboratory of the Carnegie 

 Institution at Boston (Benedict and Carpenter (a)), at Cornell Medical 

 College (Williams, H. B.) and at the U. S. Department of Agriculture 

 (Langworthy and Milner) some slight modifications of the original plan 

 have been made and these will be described here so far as the arrangements 

 for ventilation and determination of the respiratory exchange are con- 

 cerned as if belonging to the original construction at Middletown. 



The metal walls of the chamber and the ventilating pipes which con- 

 sist of metal or heavy rubber confine the air to a definite volume and to 

 allow for expansion or contraction of the air volume as the result of pres- 



Fig. 6. Diagram of the system of ventilation in 

 the closed-circuit apparatus of Atwater and Benedict. 

 The direction of the air is indicated by arrows. 



