1-24 



ELECTRO-PHYSIOLOGY 



CHAP. 



suited to experimental requirements. Hering (11) made the 

 secondary coil rotate round a vertical axis in front of the primary, 

 which was traversed by a constant current, giving rise to uniform 

 induced currents since, with the coils at right angles, induction 

 is at zero, and with other definite inclinations of the coils 

 corresponding definite induction currents make their appearance. 



Griitzner (12) subsequently investigated the physiological 

 action of currents from a Stohrer's machine, in which two 

 wire-coils with iron axes revolve in front of a powerful horse- 

 shoe magnet. Each revolution yields four currents, correspond- 

 ing as two pairs in respect of time-distribution. If 8 and N 

 (Fig. 175) are the poles of the magnet, and I and // the coils 



FIG. 176. (After Griitzner.) 



FIG. 175. 



rotating round the axis A, then when they have shifted ^ 

 revolution clockwise from this position, so that / is opposite N, 

 the first current rises gradually from 0. If / is then moved 

 away from N, the falling current alters instantaneously in the 

 reverse direction. Rising suddenly, it gradually falls to zero, 

 and then rises again equally gradually to its former height, as 

 the coil / travelling through all three quadrants approaches S, the 

 south pole. This is succeeded by an abrupt rise of current in the 

 reverse direction, so that (as shown by the accompanying curves, 

 Fig. 176) two gradually and two abruptly rising currents appear 

 with each revolution. This can be elegantly demonstrated (after 

 Griitzner) if the platinum-point electrodes are drawn at uniform 

 speed over paper moistened with iodide of potassium during the 

 revolution of the apparatus. The resulting electrolytic curves 

 appear as lines which are correspondingly thicker at the apexes 

 of the curves than in the rest of the tracing. The gradually 

 rising currents are represented by lines, small at first, and after- 



