OF BODY AND SPACE. 161 



The immediate incentive in instinctive action seems to consist in simple impressions of one 

 or other of the senses, the influence of the sensation in inciting to action being sometimes 

 matter of direct intuition, while at other times it can only be inferred from seeing that the 

 sensation is the immediate antecedent of the instinctive action ; but in either case the connexion 

 between the sensation and the corresponding exertion is as profound a mystery as that between 

 the physical affection of a special organ in sensation and the sensible experience of the 

 organised being. When I draw my breath after holding it as long as I conveniently can, I am 

 conscious of being immediately actuated by the extreme and rapidly increasing uneasiness 

 I suffer, and not from any conviction of danger to be apprehended from a further continuance 

 of the experiment. We observe that the infant begins to suck the moment the breast is placed 

 between his lips, before he can have any knowledge of the mechanism of his mouth or any 

 notion of the gratification to be attained by the exertion ; but how the sensation of touch upon 

 his lips (and probably also the accompanying smell) can induce the exertion of muscular power 

 is a question beyond the reach of human investigation. 



Again, if we place our finger within the palm of the hand of a very young infant unseen 

 by him, even when his attention is engaged in another quarter, we shall find that he will imme- 

 diately grasp our finger, of which his only intimation must arise from the sensation of touch 

 produced by contact of the foreign body. On the other hand, we see him instinctively with- 

 draw his limb from a burn or irritation of a painful nature at a period when, as remarked by 

 Sir C. Bell, he makes no attempt with his hand to ward off the most painful operation on any 

 other part of his body, shewing plainly that the sense of feeling alone does not originally 

 involve any conception of the bodily member in which the pain is organically seated. 



In like manner when the horse twitches the skin of his back in the place on which a fly has 

 settled, he can have no objective knowledge of that particular portion of his skin, or of the 

 muscles by the action of which the fly is shaken off, but he must be directly actuated by the 

 tickling sensation or sting of the fly. 



From these and similar facts it would appear that there is a constitutional connexion 

 between the sense of touch and the muscular system, in virtue of which the sensations of touch 

 operate as motives to muscular exertion, instinctively inciting the sentient being to make use of 

 the member in which the sensation is felt in pursuit or avoidance of the external cause of the 

 sensation, and subsequently guiding him in the voluntary execution of the like purposes. 



Now let us endeavour to place ourselves in the intellectual position of the infant at the 

 moment when he begins instinctively to close his hand upon the unseen finger. The first effect 

 of the muscular action will be an increased experience of tactual sensation, arising from the 

 larger surface of his hand brought into closer contact with our finger. But in addition to this 

 increased activity of the sense of touch, it cannot be doubted that in some shape or another the 

 infant will be cognizant of the resistance of the finger, the consciousness of which would form 

 so large a portion of our own experience if we were in his position. He cannot be altogether 

 without sense of the muscular exertion ; otherwise the contraction of his hand on our finger 

 would no more be entitled to the designation of his act than the beating of his heart or a cramp 

 in his leg. The final test of agency is the consciousness of the agent himself; and this it is 

 that leads me to say ' / breathe? but ' my heart beats f because, although the function of 

 Vol. IX. Part I. 21 



