22 



ELEMENTARY PHYSIOLOGY. III. 



fixed to the casing. The drum can be moved backward 

 or forward by hand without any re-arrangement. 



Observe the rate of revolution of the drum with high 

 and low gearing and with different connections of the 

 pulleys on the shaft and on the drum. 



Fig. 8. 



c. Sherrington drum. In this (Fig. 9), although the 

 gears may be engaged, the drum only rotates when the 

 cross-bar handle H is at right angles to its position in 



