IX 



ELECTRICAL EXCITATION OF NERVE 



129 



desired rate within a certain range, and in exact proportion 

 with the time-interval. The apparatus, which is constructed on 

 the principle of Wheatstone's Bridge, consists essentially of a 

 homogeneous circular conductor (trough filled with ZuS0 4 solution). 

 The current is led in at a b, the opposite ends of a diameter. _ A 



PIG. 181. Schema of v. Fleischl's orthorheonome. (Ellenberger, Physiologic, ii.) 



metal conductor turning on its centre runs across diametrically 

 (Fig. 181, zz), its two points with amalgamated zinc terminals 

 dipping into the trough E. The nerve is included in the circuit 

 of this rotating diameter (between c d). As often as it is in the 

 direction of the entrance points of the current AB, a certain 

 fraction of the current will pass through it; while at an angle of 

 90 (at CD} this fraction = 0. The current through the nerve 

 diminishes regularly with the magnitude of the angle (), provided 



FIG. 182. 



the resistance of the circuit is otherwise vanishing. Von Fleischl 

 showed that, with regular rotation of the rheonome, the oscillations 

 of current might be expressed in a broken line similar to 

 Fig. 182. Equal sections of the abscissa correspond with equal 

 times, while the ordinates are proportional with strength of 



VOL. II K 



