410 MESSRS. F. GOTCH AND V. HORSLEY 



CHAPTER IX. ON THE ELECTRICAL EFFECTS EVOKED IN THE SPINAL CORD BY 



EXCITATION OF THE LUMBAR NERVES. 



Section 1. Introductory. 



Section 2. Results of Preliminary Experiments. 



Section 3. Present Knowledge as to the Conduction of Afferent Impulses by the Spinal Cord. 



Section 4. -Anatomy of the Lumbar Plexus in the Cat and Monkey. 



Section 5. Method involving Intervening Sections. 



Section 6. Influence of Hemisection. 



Section 7. Section of Posterior Columns. 



A. Both Columns. 



B. Column same side as Nerve. 



C. Column opposite side to Nerve. 



D. Section some time previous to observation. 

 Section 8. Section of the Lateral Columns. 



Section 9. Summary of Results. 



SECTION 1 . INTRODUCTORY. 



The presence of excitatory processes in the bundles of nerve fibres which compose 

 the spinal cord is characterised, as the experiments detailed in the preceding section 

 have shown, by very definite electromotive changes. It is thus possible to extend 

 the field of enquiry which the estimation of the amount and character of these 

 changes has opened up, so as to embrace not merely the relations of the fibres in one 

 portion of the cord to those in another portion, but the relations of these to the 

 entering and issuing nerves. The importance of obtaining some definite data with 

 reference to these questions will be obvious when it is remembered that there is 

 hardly any subject in which the evidence is at once so conflicting and so unsatis- 

 factory as that of the paths by which afferent and efferent impulses travel from and 

 to their respective nerve roots. If the present method of observing the excitatory 

 electromotive effects is a trustworthy guide to the presence and amount of nerve 

 impulses in the particular region connected with the galvanometer or electrometer, 

 then there is every hope that its application in experiments, designed to show the 

 relations now referred to, will be one from which definite results may be expected. 

 How far this is borne out the following experimental details will indicate, but it may 

 be at once stated that the procedure has not belied its promise, and that, by applying 

 still more accurate and delicate methods of the same kind, there is every reason to 

 suppose that in the future results still more definite will be obtained, and that the 

 actual differentiation of the afferent from the efferent fibres in their course through the 

 bulbo-spinal system will thus be arrived at. In this manner another method will be 

 secured for research into the anatomy of the central nervous system. 



We must again note that there are two considerations concerning the functional 

 causation of any excitatory process in the cord, that of pure conduction in fibres, and 



