Manchester Memoirs, Vol xlii. {\^g%\ No. V^. 27 



ordinary nervous impulse must not be considered as the 

 only kind of event even in an ordinary nerve. That warn- 

 ing may be emphasized when we are dealing with the 

 structures of which 1 am now speaking. We may perhaps 

 go so far as to say that we probably err in supposing that 

 a visual sensation is the result of a nervous impulse, a 

 something with a definite length and amplitude of wave, 

 sweeping up from the corpus geniculatum to the occipital 

 cortex, leaving the one to pass to the other, and only 

 producing its effect when it reaches its goal. It is more 

 probable that the two structures, the cortex and the 

 lower body, in some way work together, and that a visual 

 sensation of a complete character is an expression not of 

 the cortex being affected by something merely passing to 

 it from the lower body, but of something passing to and 

 fro between the two. If it be permitted to adopt a 

 popular phraseology, we may say that the seat of visual 

 sensation is not in the cortex alone, but in the cortex 

 and the lower bodies. 



Before, however, we consider this matter any further, 

 let me turn to the cortex itself, to the occipital cortex. (I 

 will continue to use the general term " occipital cortex," 

 because, in the first place, the topographical limits of the 

 particular areaof the wholeoccipitalregion which is specially 

 concerned in vision has not, as yet, been exactly determined, 

 and, in the second place, such topographical exactitude is not 

 necessary for the theme which I have in hand.) The domi- 

 nant structural feature of the whole cerebral cortex is the 

 multitude of linkages between dendrites and the terminal 

 branchings of axons. And this is, perhaps, especially true 

 of the occipital cortex. Cells of different form send out 

 in various directions much-branched, far-reaching den- 

 drites, and intertwining with the apparently inextricable 

 tangle thus constituted run a multitude of branching axons, 

 partly belonging to cells lying in the cortex itself, partly 



