ELECTEIZATION BY REFLEX ACTION. 



123 



be either direct or inverse. In fact, each intermission of the 

 induced current (of the second coil) is produced by two successive 

 currents travelling in contrary directions. The intermissions pro- 

 duced by all the ordinary rheotomes described in the sequel (the 

 toothed wheel and the tremblers) afibrd these alternations. But it 

 is sometimes desirable to avoid the alternations, especially in 

 certain physiological experiments, or in therapeutical applications, 

 where it is wished to pass only a direct or an inverse current. In 

 order to fulfil this indication, I had made, some twelve years ago. 

 an instrument which is a modification of the wheel of Abria, 

 joined to a commutator of the poles. This instrument is repre- 

 sented in fiff. 40. 



Fig. 40. — Distributor of the entrance and issue of induction currents, and commutator of the poles. 



Like the wheel of Abria, it is composed of two toothed wheels, 

 A, B, the teeth being alternately of wood and of brass. In the 

 figure the shaded teeth rejDresent those of wood, and the unshaded 

 those of metal, mounted upon the same axis, but insulated ; the 

 brass teeth of each wheel communicate with the brass mounts 

 8 and 16, in which turns the wooden axle common to both the 

 wheels, which move together (thus differing from the instrument 

 of Abria, in which the wheels turn independently). The two 



