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CALORIMETERS FOR STUDYING RESPIRATORY EXCHANGE, ETC. 



released by an electro-magnet F, which when magnetized exercises a pull on 

 the iron rod, extends the spring E, and simultaneously releases the pressure 

 on the rubber tube at L. To make the control perfectly automatic, the 

 apparatus shown on the top of the tension-equalizer J is employed. A wire 

 ring, with a wire support, is caused to pass up through a bearing fastened 



Fig. 32. — Part of the oxygen cylinder and connections to tension-equalizer. At the left is shown the 

 upper half of the oxygen cylinder with a detail of the electro-magnet and reducing-valve. D is the 

 cylinder; K, the band supporting the oxygen cylinder and electro-magnet arrangement; F, the 

 electro-magnet; E, the tension spring; and L, the rubber tubing at a point where it is closed by the 

 clamp. The tension-equalizer and the method of closing the circuit operating it are shown at the 

 right. C and C are two mercury cups into which the wire loop dips, thus closing the circuit. B 

 is a lever used for short-circuiting for filling the diaphragm J. G is a sulphuric-acid container; H, 

 the quick- throw valve for shutting off the tension equalizer J; M, part of the ingoing air-pipe; N, a 

 plug connecting the electric circuit with the electro-magnet; and O, a storage battery. 



to the clamp above J. As the air inside of the whole system becomes 

 diminished in volume and the rubber cap J sinks, there is a point at which a 

 metal loop dips into two mercury cups C and C, thus closing the circuit, 

 which causes a current of electricity to pass through F. This releases the 

 pressure at L, oxygen rushes in, and the rubber bag J becomes distended. 

 As it is distended, it lifts the metal loop out of the cups, C and C, and 

 the circuit is broken. There is, therefore, an alternate opening and closing 

 of this circuit with a corresponding admission of oxygen. The exact posi- 

 tion of the rubber diaphragm can be read when desired from a pointer on a 

 graduated scale attached to a support holding the terminals of the electric 

 wires. More frequently, however, when the volume is required, instead of 



