832 OP THE FUNCTIONS OF THE NERVOUS SYSTEM. 



are concerned in psychical changes ; whilst it has the least influence over the 

 automatic actions of those lower centres which minister solely to the functions 

 of the bodily organism. 



in. The Cerebrum is the material organ, through whose instrumentality all 

 the processes of Thought are carried on. These processes are first called into 

 activity by impressions conveyed to the vesicular matter of the Cerebral surface, 

 by ascending nerve fibres which proceed to it from the Sensory Ganglia; and 

 the influence of that activity is retransmitted to the Sensory G-anglia by a con- 

 verse set of descending fibres. 1 There is much reason to consider that, until 

 such retransmission has taken place, the consciousness is not so affected by 

 Cerebral changes as to give to the results of these changes & psychical character; 

 for the central Sensorium appears to stand in precisely the same anatomical and 

 physiological relation to the vesicular matter of the Cerebral surface that it 

 does to the vesicular matter of the Retina or other peripheral expansions of the 

 Sensory nerves ; and there is strong analogical ground for the belief that the 

 process by which the Mind is rendered conscious of changes in the Cerebrum, 

 is performed by the same instrumentality as that by which it is made acquainted 

 with impressions on the Organs of Sense. And this view is confirmed by the 

 fact that automatic changes may take place in the Cerebrum, without any con- 

 sciousness on our own parts, the results of which, when we are at last made 

 conscious of them, correspond with those that we ordinarily attain by processes 

 whose successive steps excite as many successive states of consciousness. 



IV. These Cerebral changes, then, acting downwards upon the Sensorium, 

 give rise to those changes in our consciousness which we designate as Mental 

 Processes. These processes called into activity by Sensorial changes ranging 

 from the simple act of Perception to the highest operations of intellectual 

 power consisting also in the play of Fancy and Imagination, and including 

 those active states known as Passions, Emotions, Moral Feelings, Sentiments, 

 &c. must be regarded as essentially automatic in their nature, and as the 

 manifestations of the " reflex" activity of the Cerebrum ; since we have abund- 

 ant evidence that they can take place without any self-direction on the part of 

 the individual, who, whilst his Will is in abeyance, is in the condition of an 

 animal entirely governed by Instinct. There is, however, far less of uniformity 

 in these " reflex actions" of the Cerebrum, than we observe in those reflex 

 actions of other parts of the Nervous System, which give rise to the movements 

 ordinarily designated as instinctive ; this diversity seems partly attributable to 

 differences in the original constitution of different individuals ; but it is cer- 

 tainly due in great part to differences in the acquired constitution of the organ, 

 arising out of the mode in which it has been habitually exercised this being 

 dependent, on the one hand, on the circumstances in which the individual has 

 been placed ; and, on the other, on the use he has made of his Will. 



V. When the power of the Will has been duly cultivated, it acquires so com- 

 plete a domination over the automatic actions of the Cerebrum, that it can regu- 

 late the course of thought and the degree of emotional excitement ; intensifying 

 some of these actions, and repressing others, by determinate efforts directed with 

 a special purpose. Its power is so far limited, however, that it can only select 

 from the objects which spontaneously present themselves to the consciousness, 

 those which it desires to retain and employ ; and has no direct power of bring- 

 ing before the mind any object not actually present to it. Hence it is that, 



1 The structural distinctness of these two sets of fibres must be admitted to be hypothe- 

 tical, and it is improbable that any anatomical evidence can ever be attained, by which 

 the hypothesis may be established. But all the analogy of the afferent and efferent fibres 

 throughout the body is opposed to the idea that the same fibres can serve both purposes. 

 Whatever may be thought of their structural distinctness, however, there can be no rea- 

 sonable doubt of the transmission of nerve-force in the two directions above indicated. 



