14 CALORIMETERS FOR STUDYING RESPIRATORY EXCHANGE, ETC. 



would have general use in experiments during rest and, indeed, during 

 experiments with the subject sitting quietly in the chair. 



It may well be asked why the first calorimeter was not constructed of 

 such a type as to permit the subject assuming a position on a couch or 

 sofa, such as is used by Zuntz and his collaborators in their research on the 

 respiratory exchange, or the position of complete muscular rest introduced 

 by Johansson and his associates. While the body positions maintained by 

 Zuntz and Johansson may be the best positions for experiments of short 

 duration, it was found, as a result of a large number of experiments, that 

 subjects could be more comfortable and quiet for periods of from 6 to 8 

 hours by sitting, somewhat inclined, in a comfortable arm-chair, provided 

 with a foot-rest. With this in mind the first calorimeter was constructed 

 so as to hold an arm-chair with a foot-rest so adjusted that the air-space 

 between the body of the subject and the walls of the chamber could be cut 

 down to the minimum and thus increase the accuracy of the determination 

 of oxygen. That the volume has been very materially reduced may be seen 

 from the fact that the total volume of the first calorimeter to be described 

 is less than 1,400 liters, or about one-third that of the Middletown apparatus. 



GENERAL CONSTRUCTION. 



A horizontal cross-section of the apparatus is shown in fig. 7, and a 

 vertical cross-section facing the front is given in fig. 8. Other details of 

 structural steel are seen in fig. 9. 



In constructing the new chambers, the earlier wood construction, with its 

 tendency to warp and its general non-rigidity, was avoided by the use of 

 structural steel, and hence in this calorimeter no use whatever is made of 

 wood other than the wood of the chair. 



To avoid temperature fluctuations due to possible local stratification of 

 the air in the laboratory, the calorimeter is constructed so as to be prac- 

 tically suspended in the air, there being a large air-space of some 76 centi- 

 meters between the lowest point of the calorimeter and the floor, and the 

 top of the calorimeter is some 212 centimeters below the ceiling of the room. 

 Four upright structural-steel channels (4-inch) were bolted through the 

 floor, so as to secure great rigidity, and were tied together at the top with 

 structural steel. As a solid base for the calorimeter chamber two 3-inch 

 channels were placed parallel to each other 70 centimeters from the floor, 

 joined to these uprights. Upon these two 3-inch channels the calorimeter 

 proper was constructed. The steel used for the most part in the skeleton of 

 the apparatus is standard 2^-inch channel. This steel frame and its support 

 are shown in fig. 10, before any of the copper lining was put into position. 

 The main 4-inch channels upon which the calorimeter is supported, the tie- 

 rods and turn-buckles anchoring the framework to the ceiling, the I-beam 

 construction at the top upon which is subsequently installed the large balance 



