394 MESSES. F. GOTCH AND V. HORSLET 



AVEKAGE Effects obtained by Exciting Columns on Opposite Side to Section. 



From this table it will be seen that the electrical effects observed in the dorsal 

 region are profoundly modified by an intervening hemisection of the cord. With an 

 excitation, of minimal intensity, the application of the stimulus to the columns 

 at the dorsal end situated on the side of the section evokes little or no electrical 

 effect in the lumbar region. The interruption of the directly continuous fibres by 

 the hemisection has thus reduced the effect to such an extent, that in two Cats it was 

 completely abolished, and only present in one. 



With the same minimal intensity of stimulus, excitation of the posterior column 

 evoked no effect at all, except in one instance ; the interruption in the fibres of this 

 column thus abolishes the electrical effect. 



With a minimal stimulus, therefore, the electrical effect in the lumbar region 

 obtained by excitation of the columns in the dorsal region is dependent upon an 

 unbroken continuity in the fibres descending along the same side as the excited 

 column. It is thus clear, that not only are the stimulating induction currents which 

 traverse the excited end of the exposed column confined to that side of the cord, but, 

 in addition, that the nerve impulses generated by this stimulus travel down that side, 

 since it is the arrival of the nerve impulses at the lumbar end of the tract which 

 produces the electrical effect and this is practically abolished by the interruption 

 offered by the hemisection. 



Whilst the experiments thus furnish strong evidence against any direct and con- 

 tinuous tract of nerve fibres passing from one side of the cord to the other, the 

 presence of effects on the two sides of the cord, when evoked by more intense stimuli, 

 shows that the interruption of hemisection is not a complete block. With increasing 

 intensity it will be noticed that excitation of both lateral and posterior columns on 

 the side of section evoke electrical effects in the cord below. These must be due to 

 the passage of nerve impulses from the excited area along paths which are in relation 

 with cells, i.e., indirect, since these are the only known channels across the cord. 

 These impulses may discharge, in a reflex manner, the cellular energy of both sides 

 of the cord, the opposite side in a much less degree than the same side ; a crossed 

 electrical change would then indicate the sum of the nerve impulses evoked in the 

 opposite side by a discharge of nerve cells. Similar effects would, however, be 

 obtained if, without any reflex influence being present, an indirect path crossed from 

 the columns of one side to a column of fibres on the opposite side. Both agencies may 



