66 COMPARISONS OP RESPIRATORY EXCHANGE. 



band E is shown, and two guiding pulleys which can be adjusted so as 

 to keep the band in place with a minimum amount of friction. As 

 the metal band rises, it pushes the lever a outward, causing the ends e 

 and e to rise out of the two mercury cups c and c' . The lever a then 

 drops back into the indentation between two teeth, and the two points 

 e and e again dip in the mercury cups c and c' . Each time the points 

 dip into the mercury cups, a contact is made which closes an electric 

 circuit connected with a signal magnet, and thus each liter can be re- 

 corded as the spirometer is being filled. The mercury cups c and c' can 

 be adjusted by means of the screws d and d. When not in use the lever 

 a may be raised out of the mercury cups by means of the eccentric b. 



Device for recording the volume of inspiration or expiration. — An 

 adjustment was designed by Tissot in connection with this spirometer, 

 so that either the volume of inspiration or the volume of expiration 

 may be recorded. The arrangement is shown on a small scale in figure 

 27 at U, T. A segment of a wheel, T, is suspended loosely on the shaft 

 of the wheel F. A row of metal teeth is fastened at a point on the 

 segment T opposite the rim of the wheel F, and a rubber ring is cemented 

 in a groove on this wheel opposite to the teeth. An electro-magnet, U, 

 is fastened to the upright supporting the wheel F, the armature of the 

 magnet being attached to the arc T. A thread runs from the arc T 

 to the multiplying pulley S. The electro-magnet U is connected in a 

 circuit with the two mercury cups a and a' in the apparatus shown in 

 figure 25. 



The operation of the system when recording the volume of expira- 

 tion is as follows: The apparatus shown in figure 27 is attached to the 

 outgoing valve. When the subject inspires, the flap shown in figs. 23 

 and 25 rests against the cups a, o! (fig. 25) and the circuit thus closed 

 actuates the electro-magnet U (fig. 27) . The arc T is held motionless. 

 During expiration the flap is raised and the circuit broken. The 

 arc T moves in the same direction as the wheel F, as it (T) is held 

 against the wheel because of the friction of the metal teeth against the 

 rubber ring on the wheel F. The motion of the arc T is communicated 

 to the pulley S by a thread. At the end of an expiration, T drops back 

 to its original position, owing to the action of the electro-magnet U, its 

 circuit being closed. If a moving pointer writing on a kymograph is 

 connected to S, the movements of T may be recorded. 



GENERAL ROUTINE OF AN EXPERIMENT. 



In making an experiment by this method, the valves are first tested 

 for tightness. This may be done by inserting the nosepieces with the 

 valves attached into the nose and putting pressure against the ends 

 of the valves. Rubber tubing of about 20 mm. internal diameter 

 connects the valves with the spirometer. The valves and nosepieces 

 may be supported by means of a special cap and strings or by means of 



