186 THE THEORY OF SENSATION'. 



lo account for a phenomenon by a mere hypothesis, which itself 

 requires explanation ; for ihe difficulty is thus increased instead of 

 diminished. But the transfer of the impression on the organ along 

 the sensitive nerves, involves difficulties requiring such explanation. 

 Unless, therefore, such a transfer is well sustained by evidence to be 

 matter of fact, a theory from which this supposition is absent, is 

 simpler, and on that account to be preferred. 



Secondly. — The nerves appear from their construction and an-ange- 

 ment unsuited for such an office as the one supposed. Bearing in 

 mind the almost infinite number and variety of our sensations, as 

 well as the extreme minuteness of many of them,-together with the 

 necessity that for distinct perception the mind should take accurate 

 and unconfused cognizance of them ; the intricate convolutions and 

 interfacings of the fibres which enter into the formation of the nervous 

 plexuses appear to render them altogether unfitted for so accurate, 

 instantaneous, and minutely discriminating a transfer to the brain, 

 of the multiplicity of impressions produced by external objects on 

 the organs of sense. 



Thirdly. — There is no positive proof of such a transfer. Con- 

 sciousness gives no intimation of it. The sensation is not felt in the 

 bi-ain but in the part affected. Experiment has failed to detect the 

 supposed transmission, and no change during sensation has been 

 discovered in the state of the nerve. " Of the whole of the remarka- 

 ble process of sensation and perception," says Dr. J ohn Abercrombie, 

 ** we know nothing but the facts, that certain impressions made upon 

 the organs of sense, are followed by certain perceptions in the mind, 

 and that this takes place in some way through the medium of the 

 brain and nervous system. We are in the habit of saying that the 

 impressions are conveyed to the brain, but even in this we probably 

 advance a step beyond what is warranted. We know that the nerves 

 derive their influence from their connexion with the brain, or, as 

 forming along with it, one great medium of sensation ; but we do not 

 know whether impressions made upon the neiTous fabric connected 

 with the organs of sense are conveyed to the brain, or whether the 

 mind perceives them directly as they are made upon the organs of 

 sense." 



It has been, as we admit, well established, that a connexion with 

 the brain is necessary, but, as we have seen, it does not follow from 

 this that the impression is transmitted. Why may not the brain act 

 as the generator of influence analogous to tliat of galvanism which is 

 thence transfused through all the nerves, both of volition and sensa- 

 tion, which influence is necessary for their proper action ? Would 

 not such a supposition account for all the facts without shutting us 

 up to the admission of the transfer ? And do not some of the recent 

 facts of science tend to confirm such a supposition, shewing — not, 

 perhaps, as Dr. Wilson Philip contends, that the nervous influence is 

 galvanism — but that at least it may be analogous to it. Let it not 

 be said we are here only substituting one hypothesis in place of 

 another. We are not attempting to shew what is the nature of the 

 mutual influence of the brain and nerves, but merely contendhig that 



