236 Mr. F. Gotch and Prof. Victor Horeley. [Feb. 2( 



followed by a very de6nite and characteristic series of contractions of 

 the muscles in special relation with the particular point excited, tin- 

 effectual removal of the cortical central mechanism and subsequent 

 rvriiiition of the white fibres passing down through the internal cap- 

 sule, fec., led to the production of only a portion of the effect pre- 

 viously obtained from the uninjured brain. 



This method of observation in no wise showed what processes were 

 actually occurring in the spinal and other nerve fibres, and although 

 the ablation of the cortical centre to a certain degree suggested the 

 extent to wli ; ch the cortex acted, nevertheless it did not afford an 

 exact demon- tration of the same. Moreover, the data which the 

 graphic method furnished were precluded, through their being muscu- 

 lar records, from determining what share, if any, the lower bulbo- 

 spinal central nerve cells took, either in the production of the charac- 

 teristic sequence of contractions or in the modification, whether in 

 quality or in force, of the descending nerve impulses during their 

 transit. It seemed to us that the only way to approach this subject 

 would be to get, as it were, between the cortex and the bnlbo-spinal 

 system of centres. This would be accomplished if some means were 

 devised of ascertaining the character of the excitatory, processes 

 occurring in the spinal fibres of the pyramidal tract when, upon exci- 

 tation of the cortex, nervous impulses were discharged from cortical 

 cells, and travelled down the cord. 



The question as to the extent to which it is possible to obtain 

 physical evidence of the actual presence in nerve fibres of excitatory 

 processes, and thus to arrive at reliable data for the comparison of their 

 amounts, is one which up to the present has been answered only indi- 

 rectly, and that in two ways : first, by the extension of Helmholtz's 

 classical experiment of determining the rate of transmission, and, 

 secondly, by observing those variations in the electrical state of nei 

 fibres which Du Bois-Reyniond discovered to be an invariable 

 comitant of the excitatory state. As will subsequently be shown 

 the historical retrospect, it is well known, through the researches 

 Dn fiois-Reymond and others, that the fibres of the spinal cord, j 

 as nerve fibies in the peripheral trunks, are characterised by showing, 

 when uuexcited, an electrical difference between their longitudinal 

 surface and cross sections ; and, furthermore, that when excited, a 

 well-marked diminution of this resisting electrical state is produced 

 in the fibres of the cord, as in those of nerve trunks. Now, since 

 such excitatory variations in the electrical state are presumably paral- 

 lel in time and amoant with the presence in the nerve of the series of 

 unknown processes, termed excitatory, which a series of stimuli 

 evokes, it was reasonable to presume that, if the cortex were dis- 

 charging a series of nerve-impulses at a certain rate down the 

 pyramidal tract, there wonld be a series of parallel changes in the 



