CHAP, ii.] THE BRAIN. 1033 



part, and probably a greater part of the fibres sweeping up from 

 the subjacent white matter, whether they be fibres of the pedal 

 and tegmental systems or callosal or ' association ' fibres, end in 

 the grey matter in some other way than by bodily being continued 

 into the cell substance of cells ; they plunge into and break up 

 within the network, of which fibrils no less than cells form a 

 conspicuous part ; and we may here repeat the remark which 

 we made in speaking of the cerebellum concerning the actual 

 continuity of the elements of the network. Moreover, besides the 

 vertical fibres obviously coming from the subjacent white matter, 

 we have in this grey matter to deal with the fibres of horizontal 

 and other directions, which may come from white matter, not far 

 off, but which may come from some neighbouring grey matter; 

 our present knowledge will not enable us to settle this point. 



In the spinal cord we were able to divide all the fibres into 

 afferent and efferent respectively ; though even here we met with 

 some difficulty. Dealing with the cerebral cortex, which as we 

 have already seen is certainly especially concerned in voluntary 

 movements and in the development of full sensations, we may be 

 tempted to consider the fibres connected with the grey matter as 

 similarly divisible into motor and sensory ; and we may go on to 

 suppose that the fibres joining the cortex as axis cylinder pro- 

 cesses of recognisable cells are motor fibres, and that all the other 

 fibres joining the grey matter in some other way are sensory fibres. 

 But in doing so we are going beyond our tether ; in all probability 

 the nervous processes going on in the cortex are far too complex to 

 permit such a simple classification of the functions of fibres as that 

 into motor and sensory ; and any attempt to arrange either fibres 

 or regions of the cortex as simply motor or sensory is probably 

 misleading. But we shall have to return to these matters when 

 we deal with the functions of the cortex. 



