TISSOT METHOD. 63 



The very thin metal flap rises when the air is drawn in; when the 

 air is blown out this metal flap drops back in place, making a contact 

 in the two mercury cups a and a'. If wires are led from these mercury 

 cups to a signal magnet and battery, the respiration can be recorded 

 on a kymograph. 



Spirometer. — The spirometers used with the Tissot method are also of 

 special design, very well made, and the parts are easily adjusted. Figures 

 26 and 27 show the 50-liter and 200-liter types respectively. The bell of 

 the spirometer, which is made of very thin copper, is cylindrical in form, 

 with a conical top, and is suspended in a water-bath between the double 

 walls of a hollow cylinder. The height of the 50-liter bell is 60 cm. and 

 the diameter 33 cm., while the height of the 200-liter bell is 73 cm. and 

 the diameter 65 cm. An opening at Z permits the insertion of a rubber 

 stopper with a thermometer and tube for sampling. This rubber 

 stopper may be removed when the spirometer is emptied after an 

 experiment. The air coming from the subject or from any other 



Fig. 25. — Apparatus for registering the respiration-rate used with the Tissot method. 

 The flap has attached to it two platinum points which dip into the mercury-containing cups 

 a, a'; the flap rises and falls at each respiration. 



source enters the spirometer at the bottom through a three-way 

 cock, A. This three-way cock may also be so turned that the air 

 passes out into the room. The major portion of the weight of the 

 spirometer bell is counterpoised by the weight R. The automatic 

 adjustment of the counterpoise is, however, accomplished in the follow- 

 ing manner: A glass cylinder, C, is made of such size that when filled 

 to the level of the water in the spirometer, the weight of water in the 

 cylinder exactly equals the increase in weight of the spirometer bell, 

 due to its new position. When the bell rises or falls, water is added to 

 or taken from the cylinder C by means of the siphon tube D. Any 

 increase or decrease in the weight of the bell due to the varying dis- 

 placements of the volume of water by the mass of metal in the spirom- 

 eter bell is thus exactly counterpoised by a like increase or decrease in 

 the weight of the water in the cylinder. The bell and the cylinder C 

 are supported by means of a thin steel band, E, which is carried over the 

 aluminum wheel F (fig. 26) or aluminum wheels F and G (fig. 27), 

 the band fitting into flat grooves in the wheels. The bearings of the 



