ON VOLUNTARY MOVEMENTS. 661 



in 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 gray 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 neighboring gray 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. Deal- 

 ing 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 gray 

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

 suppose that the fibres joining the cortex as axis-cylinder processes of recog- 

 nizable cells are motor fibres, and that all the other fibres joining the gray 

 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. 



ON VOLUNTARY MOVEMENTS. 



566. When we examine ourselves we recognize certain of our move- 

 ments as " voluntary ;" we say that we carry them out by an effort of the 

 " will." And when we witness the movements of other people or of animals 

 we regard as also voluntary such of those movements as by their characters 

 and by the circumstances of their occurrence seem to be carried out in the 

 same way as our own voluntary movements. Even in the case of some of 

 our own movements we are not always clear whether they are really volun- 

 tary or no ; and in the case of other people and of animals it is still more 

 difficult to decide the question. It would be out of place to attempt to dis- 

 cuss here how voluntary movements really differ from involuntary move- 

 ments, or, in other words, what is the nature of the will ; we must be content 

 to take a somewhat rough use of the words " voluntary," " volitional," and 

 " will " as a basis for physiological discussion. We may, however, remark that 

 as far as the muscular side of the act, if we may use such an expression, is 

 concerned, a voluntary movement does not differ in kind from an involun- 

 tary movement. It is perfectly true that a skilled man may by practice 

 learn to execute muscular manoeuvres which he would not have learned to 

 execute had not intelligent volition been operative within him ; but our own 

 experience teaches us that many more or less intricate movements which have 

 undoubtedly been learned by help of the will may be carried out under cir- 

 cumstances of such a kind that we feel compelled to regard them as, at the 

 time, involuntary ; and it may at least be debated whether every movement 

 which we can carry out by an effort of the will may not appear, under ap- 

 propriate circumstances, as part of an involuntary act. In the case of the 

 lower animals, in the frog deprived of its cerebral hemispheres, for instance, 

 we have seen that voluntary differ from involuntary movements, not by 

 their essential nature, but by the relation which their occurrence bears to 

 circumstances. We have, therefore, to seek for the distinction between 



