400 



MESSRS. F. GOTCH AND V. HORSLEY 



INTERVENING Hemisection on the Left Side. 



&quot;Minimal&quot; Stimulation. In the first Cat (375) the &quot;minimal&quot; stimulation in the 

 lumbar region of the lateral and posterior columns on the side of the section evoked 

 no appreciable effect in the dorsal region, the negative result thus confirming our 

 previous conclusion, that the direct fibres in these columns are completely confined 

 to one side of the cord. This, it may be pointed out, is strictly in accordance with 

 the present state of minute anatomical knowledge, as obtained by the study of the 

 degeneration and developmental histological changes. 



Averaye of Effects with Maximal Stimulation. With the maximal stimulus, no effect 

 was evoked by the stimulation of the lateral column on the side of the interruption. 

 This contrasts with the fact that when the nerve impulses are propagated down the 

 cord, as in the previously described experiments, such stimulation evoked appreciable 

 effects. 



The remaining columns gave average effects of 



44 for the posterior column on the side of the section, 

 110 ,, lateral ,, opposite to the section, 



87 ,, posterior on the opposite side. 



The posterior column thus contains indirect fibres which come into relation with 

 cells, but through these with fibres in the column on the opposite side of the cord, and 

 this connection is such, that apparently it offers less resistance to the passage of 

 ascending or afferent impulses than it does to that of descending ones, or possibly 

 special facilities exist for the discharge of cells in response to impulses ascending in 

 the posterior column. 



B. Influence of Section of Posterior Columns. 



The influence of the section of both posterior columns upon the effect evoked by 

 excitation of the lumbar cord was studied in the case of such lesions made upon three 

 animals (Cats), in two of which the section was carried out at the time of experiment 

 at the level of the 12th dorsal, whilst in the third it was done 28 days before at the 

 level of the 10th dorsal vertebra. The results are displayed in the following table : 



