302 Journal of Agricultural Research voi. v. No. s 



will prevent the accurate measurement of the amounts of the different 

 gases in the air inclosed. Its walls must be absolutely air-tight, because 

 any leakage of air would nullify the determination of the respiratory 

 exchange, and there must be no passage of heat through them, because 

 any transference of unmeasured heat into or out of the chamber would 

 introduce error into the determination of the amount of energy produced 

 within it. In the following pages the construction of the chamber of the 

 apparatus is described, and the auxiliary apparatus and methods em- 

 ployed in determining the respiratory exchange and energy production 

 of a subject in the chamber are explained in detail. 



CONSTRUCTION OF THE RESPIRATION CHAMBER 



The respiration chamber is approximately 1.96 meters long, 1.96 

 meters high, and i . 1 9 meters wide, the total volume of the empty chamber 

 being close to 4,570 liters. On the side walls are hooks for clothing and 

 shelves for books, food receptacles, and the like. The furniture consists 

 of a chair and a table, and a cot is provided in experiments lasting a day 

 or more. These may be folded into small bulk when not in use, to pro- 

 vide as much space as possible in which the subject may move about, if 

 the nature of the experiment allows freedom of muscular movement. 

 In experiments of several hours' duration, when the subject is to be very 

 quiet, the ordinary chair and the cot are replaced by an adjustable re- 

 clining chair in which he may sit or recline at will, the change in position 

 involving almost no effort. When the experiment involves the per- 

 formance of muscular work, an ergometer of special construction for 

 measuring the amount of muscular work done is included. There is a 

 telephone for communication between the subject inside the chamber 

 and the observer on the outside. Every provision is made for the con- 

 venience of the subject within the limits of the experimental conditions. 

 (See PI. XXXV, fig. i.) 



In one wall of the chamber, facing a window of the laboratory, there is 

 an opening about 48 cm. wide by 54 cm. high, through which the subject 

 enters and leaves the chamber (PI. XXX). During an experiment this 

 is closed with plate glass sealed in place, and thus ser\'es as a window. 

 On bright days this window will admit sufficient light for reading or writ- 

 ing^but further light is generally provided by a small electric lamp inside, 

 which the subject may locate according to his desire. Near the center of 

 one end of the chamber is a smaller opening through the walls, called the 

 "food aperture," which is closed by a tube having a valve or trap on one 

 end opening into the chamber, and another on the other end opening to 

 the exterior. This comprises an air lock, through which articles such as 

 food receptacles, books, etc., may be passed into or out of the chamber 

 without any interchange of air between the interior and the exterior of the 

 chamber other than that due to displacement by the articles placed in the 



