314 



LABORATORY GUIDE IN PHYSIOLOGY. 



tambour pan, stretching the sheet rubber 

 over the spring, tying and sealing. The 

 now conical diaphragm of the receiving 

 tambour should be provided with a cork 

 button, and adjusted by passing its tube 

 through a horizontal hole near the end of 

 one of the wooden rods (see Fig. 18). 

 Connect the tambours by means of a small rubber tube. 



FIG 57. 



ii. The thoracometer. 



If one wishes to measure the extent of the movements 

 of the thoracic walls the stethograph, for mechanical 





FIG. 58. 



FIG. 58. Receiving button for Thoracometer an instrument for use in 

 quantitative determination of variations in thoracic diameters. 



reasons too apparent to need enumeration here, affords, in 

 the height of the recorded waves, unreliable data. To 

 make a quantitative determination of the variation of any 

 diameter of the thorax requires the application of a differ- 

 ent principle. The following method has been success 

 fully used: Construct the apparatus shown in the accom- 

 panying cut, using for the spiral spring brass wire 1.5 to 2 

 mm. in diameter. The cone denned by the spring should 

 be 6 or 7 cm. across the base and should have an altitude 

 from the base to the contact surface of the hard rubber 



