28 HABIT AND INTELLIGENCE, [cHAP. 



nerves ; and I think it is in the highest degree probable, 



that those nerve-fibres which connect the various parts of 



the ganglionic substance of the cerebrum with each other 



Nerves of are the nerves of thought. The sensory ganglia are, as I 



thoug it. i^qIIq^q ^i^g seat of consciousness ; the cerebral hemispheres 



The 



sensory are the seat of thought ; and I think we may consequently 

 ganglia are conjecture, with great probability, that unconscious thought 

 conscious- is due to nerve-currents flowing between various parts of 

 ^'^^^' the cerebral hemispheres, without entering the sensory 



ganglia ; and that consciousness of thought is due to other 

 currents, set in motion by these, and flowing from the 

 cerebral hemispheres along the nerves of consciousness to 

 the sensory ganglia. Owing to the remarkable power that 

 nerve-currents have of setting one another in motion, 

 currents in the nerves of thought generally start currents 

 in the nerves of consciousness, and thought becomes con- 

 scious ; but this is not always the case. Both sensation 

 Conscious- and thought are, I believe, in their own nature unconscious ; 

 thought, ^^^ t^6 nerve -currents of sensation and thought give rise 

 how pro- to consciousness, not always, and not directly, but only by 

 causing secondary nervous currents to flow along the 

 nerves of consciousness. 



My answer to the question I have asked above is con- 

 sequently this : that consciousness of sensation is due to 

 currents flowing along the nerves of the brain, upwards, 

 from the sensory ganglia to the ganglionic substance of 

 the cerebrum; and consciousness of thought is due to 

 currents flowing in the opposite direction, or downwards, 

 along the same nerves, from the ganglionic substance of 

 the cerebrum to the sensory ganglia. In both cases, not 

 the cerebrum, but the sensory gangha, are the seat of 

 Seat of consciousness ; or, in other words, consciousness is due 

 to the mutual action of the sensory ganglia and the nerve- 

 fibres which connect them with the ganglionic substance 

 of the cerebrum. 



The foregoing theory of consciousness affords a complete 



Memory, account of the physical conditions of Memory. If it is 



admitted that the consciousness of a sensation is not the 



same thing with the sensation itself, it will necessarily 



conscious- 

 ness. 



