314 MESSRS. F. GOTCH AND V. HORSLEY 



being '029 and "01 in the case of the left side, and '027 and '014 in that of the right 

 side. 



In the Monkey, the average result for the left side is '016, that for the right 'Oil. 

 It will be noticed that in each animal the sum of the two readings is slightly larger 

 than the average for the unsplit. cord. 



A further table (4) give the results of a similar splitting operation carried out on 

 the upper end of the lower peripheral fragment of the divided cord in two Cats. 



In one Cat (137) the left half of the split cord showed a resting difference of '007, 

 and the right '016 ; in the other Cat (143) the left half showed '021, and the right 

 '013. The amounts are considerably below those just mentioned, one reason doubtless 

 being the fact that the portion of cord upon which the operation was carried out was 

 severed from the brain. 



(c.) Cord previously operated upon. It has already been pointed out that, while 

 severance from the brain seems to induce a condition in the separated cord in which 

 the amount of the resting difference is less than it otherwise would have been, further 

 operations upon this severed fragment do not seetn to notably affect the difference, 

 provided they are made in such situations as to leave a part of the cord both intact 

 and in situ between their seat and the portion observed. 



That is to say, the difference in the lower fragment of a cord severed from the brain 

 is not further diminished by exposing it again in its continuity and performing there 

 either section of one or of several columns. 



It is different, however, when such operative lesions have been performed several 

 weeks before the experimental investigation. In these cases the average amount 

 of the resting difference observed was '022 Daniell, that is less than the normal, 

 but the differences between the experiments are best shown by reference to the column 

 in Appendix B., III. (5). They will then be found to vary between '012 (cord one 

 month after section of posterior roots), and '038 (cord four months after hemisection 

 on left side). This last is an exceptionally high result when compared with that 

 obtained after a very similar two months' previous hemisection when the amount of 

 the difference was only '017, and also that obtained after a one month's previous hemi- 

 section on the opposite side, when the amount was '018. 



In a case of one month's previous lesion of both posterior columns, the amount of 

 the resting difference was found to be '022, and after a lesion of one posterior column 

 it was found to be '025. 



If '030 is taken as the average amount of the difference in the normal Cat, after 

 severance of the cord from the brain, then a descending series occurs in these cases, as 

 shown in the table, in all of which with one exception the demarcation current is 

 below the normal, and the average of these, when this exceptionally high and contra- 

 dictory result is excluded, would be - 019 Daniell. 



