ON THE MAMMALIAN NERVOUS SYSTEM. 363 



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

 THE EXCITATION OF THE VARIOUS PARTS OF THE SAME. 



Section 1. Introductory. 



Section 2. Propagation of Impulses by the fibres of the Cord. 



Section 3. General characters of electrical effects in the Cord following its excitation. 



Section 4. Excitatory electrical effects in the Cord, as evidenced by the Electrometer. 



Section 5. Electrical effects evoked by localised stimulation of the Spinal Cord ; plan of 



experiments. 



Section 6. Electrical effects in the Lumbar Cord, following excitation of the Dorsal Cord. 

 Section 7. Electrical effects in the Dorsal Cord, following excitation of the Lumbar Cord. 

 Section 8. Electrical effects in each half of the divided Cord. 

 Section 9. Influence upon electrical effects in the Cord of intervening sections of the various 



columns. 

 Section 10. Summary of results of experiments. 



SECTION 1. INTRODUCTORY. 



The electrical changes produced in the cord by excitation of the cortex, and of the 

 fibres of the corona radiata, whilst due to the passage of nerve impulses along 

 tracts in the spinal cord, derive their interest from the further knowledge which they 

 give us with reference to the functions of the excited parts in the encephalon from 

 which those impulses spring. 



It is otherwise with the material of this and the succeeding chapters ; since 

 the electrical changes, now to be described, are evoked by the excitation either of the 

 different parts of the cord itself, or its nerves. The method of determining the 

 characters of the functional activity of nerve tissue, by the study of those electrical 

 effects which undoubtedly accompany and indicate the extent of that activity, is thus 

 to be now applied solely with relation to the cord. 



Since the functions of the cord are naturally divisible into those connected 

 especially with its fibres conductivity and those connected especially with the 

 activity of its cells, of which reflex action is the example, the present method was 

 applied in any given experiment with special reference to the elucidation of one of 

 these two branches of enquiry, it being always borne in mind that, as a, matter of 

 fact, the tw T o groups of function overlap.. 



The question of the localisation of paths, in the fibres of the cord alone, has at 

 present been only approached in reality by the method of histological experiment, 

 including the embryological and degeneration methods, since previous physiological 

 observation, relying on movement as an index, has always included the whole of the 

 neuro-muscular mechanism. 



The sole method for obtaining actual indications of the conduction of physiological 

 processes in the fibres of the cord, is that of determining the presence in them of 

 excitatory electrical changes. We have, therefore, carried out a very large number of 



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