414 MESSRS. F. GOTCH A\D V. HORSLEY 



and WOROSCHILOFF'S experiment we have rot yet had an opportunity of observing. 

 The experiments would have to be done under curare to avoid the dragging on the 

 cord by the convulsive movements of the animal and without anaesthesia, analgesia 

 being provided for by section of the peduncles. They are, therefore, of a very special 

 kind, and involve much consideration before embarking upon them. 



SECTION 9. SUMMARY. 



We will now sum up the results of the foregoing experiments, pointing out at the 

 same time the deficiencies as well as the advantages of the method employed. 



I. Electrical changes in the lower dorsal region of the cord are readily evoked by 

 excitation of the sciatic nerve, or the posterior roots of the lumbar plexus. 



II. These changes are dependent in the anaesthetised animal on the integrity of 

 particular columns of nerve fibres stretching between the region observed and the 

 neighbourhood of the entering nerves, 



III. The total amount of electrical change is an indication of the amount of nerve 

 energy flowing up the cord from the stimulated nerve. If the total amount be repre- 

 sented as 100, then the following numbers represent approximately the amount which 

 flows up each column and which is thus interrupted by its section : 



Posterior column same side 60 



Posterior column opposite side . . . . 15 



Lateral column same side ...... 20 



Lateral column opposite side ..... 5 



IV. The flow of nerve energy up the cord is thus mainly unilateral, 80 per cent, 

 being transmitted in the channels on the same side as the entering nerve. 



V. The comparatively small amount of nerve energy which crosses into the opposite 

 side of the cord is almost entirely localised in the posterior column of that side. 



These conclusions are, it will be observed, simply confirmatory of those already 

 indicated in the preceding chapter, in which it was pointed out that no electrical 

 evidence existed of any crossing of ascending impulses in the cord from the fibres 

 in one lateral column to those of other columns ; and that the peculiarity of the 

 ascending impulses in the cord is (a) the direct path they take up the posterior 

 column of the same side, a.nd (6) the indirect path by spread from the posterior 

 column, first into the lateral column of its own side, and then across into the 

 posterior column of the opposite side. 



Finally, our experiments do not show the path taken by sensory impulses ; it 

 is possible, though hardly conceivable, that these are essentially different in quality 

 to the ones we have been studying. All we can say is" that when nerve impulses 

 are evoked in the afferent fibres of the sciatic nerve, and proceeding up these reach 

 the cord, they apparently find several paths open to them. These paths, however, 



