358 MESSRS. F. GOTCH AND V. HORSLEY 



We will first give the results obtained in the longitudinally divided cord by excita- 

 tion of one corona radiata. 



In this series of experiments we connected either half of the longitudinally divided 

 cord with the galvanometer as in the cortex experiments previously described. 



We have not yet seen any absolutely unilateral effect, as in the case of stimulation 

 of the cortex. Very often the effect in the same side of the cord was extremely 

 small (once only a trace), e.g., 4, 6, 8, &c., but it was always present. On massing 

 the results together, i.e., adding the observations in the Monkey to those in the Cat, 

 we obtained the following proportionate averages : 



Half of cord on same side as excitation of corona 14 mean of 12 observations. 

 Half of cord opposite or corresponding to the corona excited 50 mean of 13 

 observations. 



The proportion, therefore, is 7 to 2, whereas the cortex proportion is almost 5 to 1, 

 and often purely unilateral. Consequently it appears that bilateral phenomena are 

 more easily elicited by exciting the corona radiata than the cortex cerebri, provided 

 the same care is employed to avoid as far as possible in both cases errors due to 

 spread, &c. 



The explanation of this is not far to seek, and, if correct, throws more light on 

 bilaterality. It simply consists in the obvious fact that removal of the cortex lays 

 bare a crowd of association fibres, the excitability of which is heightened by the 

 section removing the cortex, and that it is the spread of the excitatory effect along 

 these fibres to other central mechanisms in the encephalon, i.e., opposite cortex, cere- 

 bellum, &c., which produces the bilateral phenomenon. It is thus extremely likely 

 that bilateral tonus should occur after stimulation of but one corona radiata. 



In accordance with what we have said before respecting the influence of ether, this 

 reagent afforded an opportunity of testing the truth of the foregoing views, since the 

 influence of bilateral central mechanisms could be by this means in part excluded, and 

 it could therefore be seen whether or no there was a corresponding modification in the 

 bilateral character of the effect. 



We found that deeper etherisation invariably tended to restore in a great measure 

 the inequality between the two cord effects, the difference between the two being 

 much greater in proportion as the degree of anesthesia increased. This again seems 

 to indicate that any markedly bilateral effect is due to an additional functional 

 activity in the cortex on the opposite side to the excited corona. 



IV. Excitation of Corona Radiata. Effect in Cord with previous Hemisection. 



It was necessary now to repeat the design of the graphic experiments as employed 

 by FRANCK, SCHIFF, LEWASCHEW, and others, using, however, our present electrical 

 method, that is to say, observing how far a hemisection of the cord between the 



