270 MESSRS. F. GOTCII AND V. HORSLKY 



the loss of function the probable paths of transmission of afferent or 

 impulses, yet such a mode of experimentation is always open to very grave 

 disadvantages and sources of fallacy. Such, for example, is the always recurring 

 possibility of functional changes proceeding beyond the desired lesion, &c. 



The accomplishment of this further purpose, viz., the localisation of both paths and 

 centres by ascertaining the excitatory electrical effects in relation with them, was one 

 of the main objects we had in view. 



In carrying it out we found it was unnecessary to employ the electrometer, and, 

 in fact, that it was advantageous to use the galvanometer, the record of which could 

 be more easily and more accurately noted, since its graduation admits of far higher 

 magnification. Moreover, with this instrument it was possible, by employing a series 

 of stimuli, of known number and duration, to obtain quantitative results of definite 

 comparative value, as will be shown further on ; and thus to compare the electrical 

 effects evoked (1) in different central paths by direct stimulation of these, and (2) in 

 any one path by excitation of different regions. 



The plan upon which the present paper is framed is, first, to give a historical 

 retrospect of the work of authors who have opened up the study of electrical 

 changes in the central and peripheral nervous system ; second, to describe at length 

 our mode of experimentation, with special reference to the modifications which 

 we have introduced, then to compare roughly the results we have obtained by our 

 present method with those which had been previously ascertained by the graphic 

 method, and so introduce the description of the facts which we have discovered, 

 elucidating the physiology of the spinal cord both in its relation to the higher centres 

 and to the peripheral nerves. In describing the detailed results of our experiments 

 we have found that it is difficult, from the extent of ground covered by the subject, 

 to adopt a convenient arrangement of facts, and mode of describing the same, which 

 are free from the fault of repetition. We finally determined to gather the results 

 together into definite groups, each associated with the excitation and investigation of 

 particular regions, and refer in the briefest manner to any important principles which 

 were not directly elucidated by, but only involved in, the particular experiments 

 under consideration. Finally, we give at length a summary of the general conclusions 

 which we consider we are justified in drawing from our experimental results.* 



* We here wish to express our great indebtedness to Professor BURDON SANDERSON for placing at our 

 disposal the instruments and equipment of the Physiological Laboratory of the University of Oxford. 

 We are also under especial obligations to Mr. G. F. BURGH, whose constructive skill provided us with 

 fie requisite electrometers, and who very kindly gave his assistance in preparing our photographic 

 resords. 



Finally Dr. HOWARD TOOTH has very obligingly carried out the laborious task of the microscopical 

 investigation of the spinal cords in those cases where we performed the section of columns antecedently 

 to the special experiments of the present research. 



The expenses of the present investigation have been defrayed by grants from the Scientific Grants 

 Committee of the Royal Society, and from the Scientific Grants Committee of the British Modical 

 Association. 



