44(i MESSRS. F. GOTCH AND V. HORSLEY 



CHAPTER X, ELECTRICAL CHANGES IX THE NERVES FOLLOWING EXCITATION OF 



THE SPINAL CORD. 



Section 1. -Introductory. 



Section 2. Plan of experimeiits and preliminary observations. 



Section 3. Electrical effects in sciatic nerve following excitation of different columns of the cord. 



Section 4. Electrical effects in afferent nerves following excitation of the cord : 



(1.) Posterior roots. 



(2.) Sciatic nerve after section of anterior roots. 



Section 5. -Electrical effects in efferent nerves following excitation of the cord. 

 Section 6. Influence upon the effects in the nerve of intervening sections of the cord. 



A. Influence of hemisection. 



B. Influence of section of the posterior column on the same side. 



C. Influence of section of the posterior column on the opposite side. 



D. Influence of section of both columns. 



E. Influence of section of the lateral columns. 

 Section 7. Summary and conclusions. 



SECTION 1. INTRODUCTORY. 



In the foregoing chapter the results have been given of the observation of a new 

 index of cord activity, that of noting the accompanying electrical effects when the 

 afferent nerves were excited together with the influence upon these of a series of 

 intervening sections. 



It will be seen that the plan of the whole of that research was upon the lines of 

 previous investigations, except as regards the index employed ; in the experiments to 

 be detailed in this section both the method and plan of experiment are entirely novel, 

 since conclusions can only be arrived at by the evidence afforded by the electrical 

 effects as indicative of the presence or absence of excitatory changes. The novelty 

 consists in this, that we are able to detect excitatory electrical effects in the 

 issuing nerves when the cord is stimulated ; not merely in the nerves them 

 selves, but in their roots. Now as far as the efferent motor roots and motor portion 

 of the mixed nerves are concerned, the method whilst giving us valuable information 

 has obvious relations with the data which have already been obtained by the graphic 

 method of recording the muscular contractions ; but as far as the afferent sensory 

 nerves are concerned, it introduces us to previously unknown relationships, for there 

 is no indication other than an electrical one at present known, which can detect the 

 passage of nerve impulses from the cord into afferent tracts, since such passage is opposed 

 in direction to that of the normal transmission as usually understood. It has been 

 already stated that one of the most valuable results of the discovery of the excitatory 

 electrical change was that set forth by DU Bois-REYMOND, as proving the propagation 

 of excitatory effects in both directions along a continuous tract of either afferent or 

 efferent nerve fibres, this being evidenced by the presence of the electrical change at 



