364 MESSES. F. GOTCH AND V. HORSLEY 



experiments upon the spinal cord under very different conditions, with the express 

 purpose before us of obtaining data which should give clear evidence of the conduc- 

 tion of nerve impulses in its fibres and centres respectively. The results furnished by 

 our experiments may be split up into the following groups : 



A. The experimental evidence of definite localisation of the channels of conduction 

 of nerve impulses afforded by electrical changes in the cord, when evoked by stimula- 

 tion of its different parts, whether distal or proximal. 



B. The evidence of the localisation in the cord of fibres which enter it by the roots 

 afforded by electrical changes in the cord when evoked by stimulation of its nerves. 



C. The evidence of the relations of the spinal cord to the nerves afforded by 

 electrical changes in the nerves, when evoked by stimulation of separate parts of 

 the cord. 



D. The experiments elucidating the complicated group of phenomena in relation 

 with the reflex activity and function of the spinal nerve cells. This may be expressed 

 as follows : 



The evidence afforded by the electrical changes, in both cord and nerve, of the 

 nature of the role of the nerve corpuscles in the cord. 



To obtain a sufficient mass of evidence, to establish even a few conclusions in these 

 four subjects, a large number of experiments have been carried out, constituting by 

 far the larger share of the work we have done since our preliminary communication in 

 the ' Proceedings of the Royal Society,' in 1888. 



The groups of data just indicated, in which these results are expressed, will be 

 treated of in the succeeding four consecutive chapters ; group A. in the present 

 Chapter VIII., B. in Chapter IX., C. in Chapter X., and D. in Chapter XI., this 

 being the order which seems to us at once the most natural and the most likely to 

 present the conclusions in a logical and thus intelligible manner. 



We therefore now pass to the consideration of the experiments, confining ourselves 

 in this chapter to the electrical changes evoked in the spinal cord by stimulation of 

 its different parts, and these only. 



It is, however, first necessary to say a few words on the general question of 

 conduction in the nerve fibres of the cord. 



SECTION 2. PROPAGATION OF IMPULSES BY THE FIBKES OP THE CORD. 



It has been maintained that the nerve fibres of the spinal cord do not respond to 

 direct stimulation, in the same way that the fibres in a mixed nerve do,* and that it 

 is the cellular elements alone which respond to excitation, the resultant nerve impulses 

 being therefore, according to this view, indirect. The experiments to be detailed in 

 this and the succeeding chapters will give convincing proof, if that is necessary, of the 



* VAN BEEN, ' Nederl. Tijdschr. v. Geneesk.,' vol. 3, 'p. 393. MOLESCHOTT, ' Unters. z. Naturl.,' 1860, 

 vol. 7, p. 380. 



