328 MESSRS. F. GOTCH AND V. HORSLEY 



muscular movement of any kind existed, yet a marked and distinct electrical change 

 of the usual kind was present in the cord and evidenced both in the electrometer and 

 the galvanometer. 



When, further, owing to prolonged excitation, exposure, or slighter degree of 

 etherisation, hyperexcitability of the cortex became established, subsequent excitation 

 evoked a more general discharge, and although the muscles of the trunk and upper 

 limb were now thrown into active contraction, the change evidenced by the electro- 

 meter and galvanometer remained similar in character to that previously observed. 



(3.) If in any given instance with the central end of the spinal cord in the lower 

 dorsal region exposed and connected with the galvanometer electrodes, the cortical 

 area for the upper limb was excited, no effect was observed in the galvanometer and 

 electrometer, although the muscles of the upper limb were thrown into convulsion. 



(4.) The injury (cutting off, &c.) of the cord between the exposed region and its 

 deep connections abolishes the effect in the cord, even although the muscles are 

 thrown .by cortical excitation into violent spasm. 



(5.) In addition to the above, the whole mass of results to be detailed in this and 

 the succeeding chapters is convincing evidence of the truth of our interpretation, 

 since, as will be seen by separating the fibres in the two sides of the cord (longitudinal 

 section), by interrupting the fibres on one side only (hemisection), &c., we obtained a 

 differentiation in our results which admits of no other explanation than the one 

 upon which we base our deductions, namely, that the electrical effects observed are 

 due to changes localised in the exposed cord, and, moreover, in the experiments 

 under discussion localised particularly in the nerve fibres which form the pyramidal 

 tracts. 



The fact above alluded to of the absence of electrical effects in the dorsal cord when 

 the area for the upper limb was excited in the Monkey, involves matters of such 

 importance that we now pass on to consider it in some detail. 



(c.) The Localisation of Efferent Representation in the Cortex as ascertained by the 

 Electrical Method. 



It was clear from the commencement of this research, that our method afforded 

 means of differentiating the centres in the cortex and their correlated fibres in the 

 spinal cord. We accordingly made observations of the following character : 



Having exposed the cortex freely, and connected, as before, the cut dorsal cord with 

 the electrometer, we proceeded to obtain the usual result by exciting the lower 

 limb area with a minimal but adequate stimulus, evoking thus an effect without at 

 the same time developing an epileptic hyperexcitability of the cortex. We then 

 explored the rest of the surface of the so-called motor region with the electrodes and 

 the same strength of excitation, to see how far we could determine whether there was 



