24 Mr. F. Gotch and Prof. Victor Horsley. [Nov. 15, 



current usually lasted for two seconds, that is about 200 equal and 

 alternately directed induction currents passed through the excited 

 tissue. During this period the mercury showed an excursion opposed 

 in direction to that of the difference between the longitudinal surface 

 and cut end of the cord. This excursion persisted as long as the 

 excitation lasted, and ceased when this was left off. Then after an 

 interval of from one to three seconds there ensued a rhythmical 

 succession of excursions each opposed in direction to the resting 

 difference, some apparently single and others multiple. These lasted 

 from twenty to thirty seconds and suddenly ceased. 



The excursions varied in amount from one to about four divisions 

 of the micrometer eyepiece, and their rate of occurrence was too rapid 

 to be correctly estimated by the eye. We therefore obtained photo- 

 graphs of this rhythmical effect, and of these we append two (see 

 figs. 4 and 5). The first of these (fig. 4) shows the electromotive 

 change occurring in the spinal cord during a complete convulsion, in 

 which may be distinguished the first persistent stage parallel to the 

 tonic stage of the muscular epileptic convulsion and the second 

 rhythmical series parallel to the clonic stage. 



They are both shown upon the plate, which in this instance 

 took about twelve seconds in travelling past the image of the 

 capillary. 



The second photograph (fig. 5), taken on a quickly travelling plate, 

 shows the rhythmical stage only. The rate of the rhythm is seen to 

 vary, and the individual variations to become more pronounced as the 

 rhythm slows, that is, towards the end of the fit. 



We have repeated this observation thirty or forty times, and feel 

 ourselves justified in concluding that we have obtained evidence that 

 during a cortical epileptiform discharge the electromotive changes in 

 the spinal cord are exactly parallel as regards the character of their 

 sequence to the convulsions of the muscles as recorded by the graphic 

 method. It remains to be stated that after removal of the cortex we 

 have obtained an effect in the electrometer when the corona radiata 

 was stimulated. This effect was only present during the period of 

 excitation, no rhythmical after-effect ever being observed. Its 

 character was prolonged, and resembled the persistent stage referred 

 to above (see fig. 6). 



In conclusion, we consider that since by the method we have 

 adopted the influence of the lumbar bulbo-spinal centres is excluded, 

 the existence of the epileptic rhythm in the dorsal regions of the 

 spinal cord points to its being almost entirely of cortical origin. 



