424 ELECTRO-PHYSIOLOGY CHAP. 



trical organ on either side of the spinal cord. " These are too 

 short to admit of a number of them being collected into a bundle, 

 while each governs too small a part of the organ to be sufficient 

 in itself" (du Bois-Beymond, 4 e, p. 187). 



In order to make the necessary preparations from Torpedo, with 

 simultaneous control of the activities of the organ, Schoiilein (30) 

 placed the animal upon a flat dish of zinc, and covered the skin of 

 the back above the organ with a second zinc plate of the same 

 shape ; a telephone in circuit with the two contacts signalled the 

 discharges. After dividing the medulla oblongata, and extirpating 

 the spinal cord, there is no difficulty in exposing the electrical . 

 nerves. Preparations consisting of the two organs and their cor- 

 responding nerves alone are somewhat more difficult. 



We have already discussed the character of the pitch, and 

 intensity of the natural discharge of Torpedo as observed in the 

 telephone. It is essentially characterised, not merely to touch 

 but also to the ear, by the same manifestations as a rapid series 

 of induction currents, so that with electrical stimulation of the 

 animal it is not always easy to separate the discharging and in- 

 variably audible currents from the shocks discharged. This, how- 

 ever, becomes possible, owing to a striking difference in pitch, if 

 with uniform distance of coil the electrodes are placed first upon 

 one of the electrical nerves, and then upon the exposed lobe. In 

 the latter case the tone swells suddenly to " the pitch of a trumpet 

 blast." With weaker stimulation, and the introduction of the 

 acoustic current-interrupter, it is often possible to hear a tone of 

 the same pitch, but different intensity. The pitch may vary with 

 repeated stimulation, and indeed during stimulation, in constant 

 oscillations. Electrical excitation of the part of the brain anterior 

 to the lobe again as a rule provokes a shock, corresponding in 

 intensity with that of the spontaneous discharges, i.e. not as a rule 

 coinciding with the stimulation frequency. As was pointed out by 

 F. Piolmiann (29), there seems in the electrical lobe of Torpedo 

 to be, as it were, a kind of localisation, i.e. a definite grouping 

 and arrangement of ganglion-cells, since only a limited portion of 

 the organ can be excited from any given point of the lobe. 



It is characteristic of every spontaneous (voluntary) or reflex 

 discharge of an electrical organ, that it is discontinuous like 

 voluntary muscular contraction, and consists of a closely-packed 

 series of short impacts of current (Marey's "flux dcctrique "), each 



