478 MESSRS. F. GOTCH AND V. HORSLEY 



the motor path (lateral column) on one side and the principal afferent path (posterior 

 column) of the opposite side. 



Finally, the results of the foregoing sections have brought to light some interesting 

 details as regards the relation of the cord to the efferent nerves. 



In the Table it will be noticed that the results, obtained with &quot; minimal &quot; stimuli, 

 as regards the sciatic nerve, are not affected by section of its anterior roots ; hence, 

 as far as the cord stimulation in these experiments extended, no nerve impulses passed 

 down the motor roots capable of causing perceptible electrical changes in the nerve 

 except with strong stimuli. 



As far, then, as the localisation of the path of efferent fibres in the cord is concerned, 

 the present investigation has at present gained no further information ; the lateral 

 column on the same side as the issuing nerve is the main path for outgoing nerve 

 impulses in the lumbar nerves. But the method has brought to light a remarkable 

 characteristic of this path, namely, that at one portion, that which connects in the 

 spinal nerve-centres the pyramidal nerve fibres with the origins of the anterior root- 

 fibres, it exercises such a modifying influence upon the traversing impulses that these 

 issue so altered in number, intensity, or quality, as to cause but very slight electrical 

 effects in the nerves, and that it is not until a comparatively strong stimulus is used 

 that the issuing impulses are of such kind as to cause really appreciable nerve effects. 



This brings us to the subject of the next chapter, which deals with the physiological 

 relations between the nerve-corpuscles and the nerve-fibres. 



CHAPTER XT. ON THE FUNCTIONAL ACTIVITY OP NERVE CENTRES AS EVIDENCED 



BY THE PRESENT METHOD. 



Section 1. The present state of knowledge of the relations of the nerve centres in the cord. 



(1). Anatomical. (2). Physiological. 

 Section 2. Experiments by the galvanometric method directly bearing on the spinal nerve centres. 



1. Resistance offered by the efferent side of the centre to the passage of impulses. 



2. Resistance offered by the afferent side to the passage of impulses. 

 Section 3. Character of the impulses discharged by the spinal centres. 



Section 4. The influence exerted upon the electrical changes in a directly-excited nerve by its attach 

 ment to the spinal cord. 



Section 5. The spread of reflex discharges up and down the cord (internuncial fibres). 

 Section 6. On the electrical changes in the cortical nerve centres. 

 Section 7. Summary. 



SECTION 1. THE PRESENT STATE OF KNOWLEDGE AS TO THE RELATIONS OF THE 



NERVE CENTRES IN THE SPINAL CORD. 



The employment of the galvanometric method to estimate quantitatively the 



