470 



MESSRS. F. GOTCH AND V. HORSLEY 



SECTION of one Posterior Column on the same side as the Nerve. Left Sciatic Nerve 



observed. 



In these two cases an intervening section of the posterior column on the side of the 

 nerve observed had the effect of entirely abolishing, or diminishing to a mere trace, 

 the large nerve electrical change which was formerly produced by the excitation of that 

 column It may therefore be inferred, that the fibres which connect the posterior 

 column at the level of the 10th dorsal vertebra with the posterior roots of the lumbar 

 nerves on the same side, run wholly in that column, and that the stimulation and the 

 path are strictly localised therein. 



There is, however, a further result, that, namely, shown by a diminution in the 

 nerve change evoked by stimulation of other columns. This may be due either to 

 the cutting off of crossing fibres, or to a depressed condition in the excitability of 

 the remaining part of the cord. 



It is improbable, however, that both the latter causes operated in these cases, 

 since when we group together in the next table the influence of the lesion upon the 

 electrical changes in the nerve of the opposite side, although we obtain in both 

 animals evidence of diminution, yet the condition of the Monkey after the section 

 was evidently one of more and not less excitability than it was before, since the 

 uninjured right posterior column evoked larger effects than it did in the normal state. 

 (See Hyperexcitability after Section, Chapter IX., Section 7, C.) 



