METHODS OF MEASUREMENT. 



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FIG. 1. Treadmill, with spirometer and various recording devices. 



The circulating air from the soda-lime containers of the respiration apparatus was conducted to 

 the subject through the pipe A, and after passing through the pipes E and F and the spir- 

 ometer G, was returned to the absorbers through the pipe H. Preliminary to the experi- 

 ment, the subject respired into the room air through the 3-way valve D by the port d. At 

 the beginning of the period, the valve D was turned and the subject was connected with the 

 circulating-air system. By means of the by-pass B, the circulating air could be deflected 

 through C and brought closer to the mouth of the subject, thus eliminating rebreathing. 

 The parts of the apparatus specially indicated in the figure are: E, rubber hose to permit the 

 adjustment of the mouthpiece to any height needed by the subject; G, spirometer with 

 ventilation adder-wheel w and kymograph Z; g, pulley for reducing the movement of the 

 pointer recording on the kymograph drum; 7, lever for operating valve D by the bar J, 

 connected by cord with arm k; L, knob supporting the arm K; M, tension spring for operating 

 valve D; N, NI, screws for adjusting the grade of the treadmill; O, spirit-level; P, motor, 

 driving mechanism not shown; Q, Q\, adjustable brake on the motor shaft; R, counter for 

 recording revolutions of front pulley; S, long wooden fork fastened to the shoulders of the 

 subject by elastic webbing; the rise and fall of this fork is transmitted by T to the step-lift 

 counter and kymograph, not shown in the drawing; U, Ui, electrodes for securing electro- 

 cardiograms of the pulse-rate; V, electrode for grounding the subject; W, W\, brass-gauze 

 brush and leads for grounding the treadmill; this brush was discarded when the method was 

 changed to that of grounding the subject by the electrode V; X, step-counter with spring 

 attached to the subject's ankle; Y, framework protecting the spirometer. 



