238 Mr. F. Gotcb. and Prof. Victor Horsley. [Feb. 2t 



and intensity were specially determined. The records were made by 

 a Thomson high -resistance reflecting galvanometer, and a Lippmanii's 

 mercurial capillary electrometer. 



The tissue, whether nerve or spinal cord, was so arranged for obser- 

 vation as to be always suspended in the air, one end remaining in 

 connexion with the animal ; consequently any error due to cnri-ent 

 deviations from the rest of the body could only have a slight and 

 unipolar effect. 



3. Resting Electrical Difference between the Cut Surface of the Tissue 



and its Uninjured Longitudinal Surface. 



The average amounts of this difference in the tissues observed were 

 as follows : 



Cat. Monkey. 



Nerve (69 cases), 0-01 Daniell ... (12 cases), 0'005 Daniell. 

 Root (5 cases), 0'025 



Cord (50 cases), 0-032 ... (9 cases), 0'022 



We have observed that the cord difference is greater when that tissue 

 is in connexion with the higher centres, and that it rises after 

 excitation. An important fall of the difference is to be remarked in 

 all three tissues as a direct result of systemic death. 



4. Electrical Changes in the Spinal Cord evoked by Excitation of 



Cortex Cerebri and Corona Radiata. 



We further discuss in our full paper the following points additic 

 to those described in our previous communication, and which hai 

 resulted from the observation of the above changes: 



(a.) Localisation of cortical areas of representation in relation 

 the various regions of the cord. 



(i.) Bilaterality of representation in the central nervous system, as 

 evidenced by the electrical changes in the two halves of the 

 spinal cord, consequent upon excitation of the brain or cord. 



5. Electrical Changes in the Spinal Cord when Evoked by Direct Excita- 



tion of its Fibres, after Severance from the Encephalon. 



We have by employment of this method ascertained the proportion- 

 ate existence of direct channels in the various columns of the spinal 

 cord, our design embracing the quantitative comparison of the elec- 

 trical changes (and so indirectly of the nerve impulses) which are 

 transmitted as a result of minimal excitation of the fibres. To further 

 control our observations on these points, we have also determined the 



