TISSOT METHOD. 



65 



aluminum wheels are steel points, fitting into sockets. The upright 

 position of the counterpoise cylinder C is determined and maintained 

 by means of two brass rods on which the cylinder travels. These are 

 firmly fastened when the cylinder is placed in position, and, when 

 properly adjusted, permit the rise and fall of the cylinder with a mini- 

 mum amount of friction. The siphon tube D is also so arranged that 

 it does not touch the cylinder C at any point. To send water into the 

 cylinder C, the three-way cock K is so turned that water flows through 

 the rubber tubes / and H (the connection with the rubber tube I being- 

 closed) and then through the siphon tube D into the cylinder. When 

 the cylinder is filled to the same 

 level as that in the tank, the three- 

 way cock K is so turned that con- 

 nection is made between the 

 tank of the spirometer and the 

 siphon. The level of the water 

 in the tank of the spirometer is 

 maintained by a constant flow 

 of water through the tube J I, 

 and into the opening L; the over- 

 flow passes out of the tank through 

 the opening M and the rubber 

 tube N. A scale is shown at the 

 right-hand side of the apparatus 

 which, in the 50-liter spirometer, 

 is divided into 0.25 liter, while in 

 the 200-liter spirometer it is di- 

 vided into 0.5 liter. The alumi- 

 num pointer fastened upon 

 the metal band above the spiro- 

 meter indicates the position of 

 the bell. The 50-liter spirometer 



may be read to 0.05 liter, and the 200-liter apparatus to 0.1 liter. 

 The movements of the bell of the spirometer when properly adjusted 

 can be made sensitive to 0.1 mm. water pressure. The cock P at the 

 bottom of the tank of the spirometer provides for emptying the tank 

 when desired. The level of the whole apparatus can be adjusted by 

 means of the leveling screws Q, Q, Q. 



Apparatus for registering the volume of air in the spirometer. A special 

 attachment upon the bar supporting the aluminum wheels permits the 

 automatic registration of each liter of gas as the spirometer is filled. 

 On the metal band, E, between and 50 or and 200, are saw-teeth 

 which are so cut that when the band moves upward it operates a thin 

 metal lever which rises and falls with the movement of the metal band. 

 This special attachment is shown in figure 28. A section of the metal 



FIG. 28. Apparatus for registering the volume 

 of air in the Tissot spirometer. 



E, portion of band supporting the bell of the 

 spirometer; a, lever actuated by the saw-teeth on 

 the band E as the bell rises ; e, e, points dipping 

 into the mercury cups c, c', as each tooth of E 

 moves upward past a; d, d, adjustment screws; 6, 

 eccentric for raising a when latter is not in use. 



