430 



MESSRS. F. GOTCH AXD V. HORSLEY 



SECONDARY Coil 500 (minimal). 



The electrical change is thus three times as large when evoked by stimulation of 

 the nerve on the side opposite to the lesion, that is, the right side, as on the side (left) 

 of the division. Hence, the major part of the change must be cut off on the left side 

 by the lesion,* that is to say, the nerve impulses, of which the change is an index, are 

 unable to ascend the cord on the left side to the observed region in the neighbour- 

 hood of the 7th dorsal, owing to the hemisection at the 13th dorsal interrupting their 

 path. If we suppose that the actual effect observed by stimulating the left nerve is 

 due to impulses which normally cross the cord, whilst that observed by stimulating 

 the right is due to impulses which do not cross, then the interruption has cut down 

 the effect which the normal excitation of the left sciatic nerve would produce from 

 92 + 31 =123 to 31, i.e., 75 per cent. 



When the stimulus was four times the intensity of the above, that is, sufficient to 

 evoke strong reflex contractions, a similar disproportion was found to exist although 

 it was not so marked. 



This is shown by the following table : 



SECONDARY Coil 2000. 



* In this animal microscopical examination of the cord showed that the lesion involved all the left 

 lateral and posterior columns, the whole grey matter, and, except its median edge, the anterior column. 

 Of ascending degeneration there was beautifully marked destruction of the left postero-median column, as 

 also of the direct cerehellar and antero-Iateral tracts, and a few degenerated fibres in the right postero- 

 median column. Of descending degeneration there was, immediately below the lesion, degeneration in 

 the left lateral pyramidal tract and also in left the anterior column. 



