FUNCTIONS OF THE SENSORY GANGLIA. 721 



from that purposive impulse which is essential to render them voluntary. This 

 is well seen in the efforts which it makes to find the nipple with its lips; being 

 probably guided thereto at first by the smell, but afterwards by the sight also ; 

 when the nipple has been found, the act of suction is purely excito-motor, as 

 already explained. So in the idiot, whose brain has never attained its normal 

 development, the influence of sensations in directly producing respondent move- 

 ments is obvious to all who examine them with discrimination; and a remark- 

 able case will be cited hereafter (Sect. 7), in which an entire though temporary 

 suspension of Cerebral power, reducing the subject of it to the condition of one 

 of the lowest Vertebrata, gave a very satisfactory proof of the independent power 

 of this division of the Encephalic centres. But we do not require to go so far 

 in search of characteristic examples of this kind of reflex action ; since they are 

 afforded, as already remarked, by the performance of habitual movements, which 

 are clearly under Sensorial guidance, when the Cerebrum is occupied in some 

 train of action altogether disconnected with them. An individual who is subject 

 to "absence of mind" may fall into a reverie whilst walking the streets, his 

 whole attention may be absorbed in his train of thought, and he may be utterly 

 unconscious of any interruption in its continuity; and yet, during the whole of 

 that time, his limbs shall have been in motion, carrying him along the accus- 

 tomed path, whilst his vision shall have given the direction to these movements, 

 which is requisite to guide him along a particular line, or to move him out of 

 it for the avoidance of obstacles. As already remarked ( 726), there seems 

 strong reason for regarding the ambulatory movements of the limbs as in them- 

 selves excito-motor; but the guidance of these movements by the visual sense 

 marks the participation of the Sensorium in this remarkable performance. It 

 has been maintained by some Metaphysicians and Physiologists that these 

 " secondarily automatic" actions always continue to be voluntary, because their 

 performance is originally due to a succession of volitional acts, and because, in 

 any particular case, it is the will which first excites them, whilst an exertion of 

 the will serves to check them at any time. But this doctrine involves the 

 notion, that the will is in a state of pendulum-like oscillation between the train 

 of thought and the train of movement; whereas nothing is more certain to the 

 individual who is the subject of both, than that the former may be as uninter- 

 rupted as if his body were perfectly at rest, and his reverie were taking place 

 in the quietude of his own study. And as it commonly happens that the 

 direction taken is that in which the individual is most in the habit of walking, 

 it will not unfrequently occur that, if he had previously intended to pursue some 

 other, he finds himself, when his reverie is at an end, in a locality which may 

 be very remote from that towards which his walk was originally destined; which 

 would not be the case, if his movements had been still under the purposive 

 direction of the will. And although it is perfectly true that these movements 

 can be at any time checked by an effort of the will, yet this does not really 

 indicate that the will has been previously engaged in sustaining them ; since, 

 for the will to act upon them at all, the attention must be recalled to them, and 

 the Cerebrum must be liberated from its previous self-occupation. And the 

 gradual conversion of a volitional into an automatic train of movements, so that 

 at last the train, once started, shall continue to run down of itself, will be found 

 to be less improbable than it would at first appear, when it comes to be under- 

 stood that the mechanism of both sets of actions is essentially the same, and 

 that they merely differ as regards the nature of the stimulus which originallv 

 excites them ( 757). That the same automatic movements are not excited 

 by the same sensations, when the Cerebrum is in its ordinary state of functional 

 connection with the Sensorium, is a fact entirely in harmoDy with the principle 

 already laid down ( 683 6). The complete occupation of the mind in other 

 ways, as in close conversation or argument, or even (it may be) in the voluntary 



