CHAPTER LIT 



THE PHYSIOLOGY OF CONSCIOUS STATES 



THERE are certain considerations, relating to the physiology of con- 

 scious states in general, to which it will be well to pay attention, 

 before we pass to a detailed study of the special senses. 



It is sometimes argued that states of consciousness are the 

 product of the activity of nerve-cells, just as bile is the product of 

 the activity of the liver-cell, or as contraction results from the 

 activity of the muscle fibre. But this analogy will not bear close 

 investigation. It is, however, true : 



(1) That the different senses are dependent for their manifesta- 

 tion on the integrity of different definitely localisable areas of the 

 cerebral cortex. 



(2) That such drugs as alcohol, caffein, and chloroform, which 

 have a known action on living substance, also affect the course of 

 conscious processes. 



(3) That disease or malformation of the brain is accompanied by 

 impairment or absence of intelligence. 



But because nervous substance is essential for the manifestation 

 of conscious states, one cannot legitimately infer that this substance 

 produces those states. Indeed, by a vast number of philosophers a 

 very different position has been upheld. So far from believing that 

 mind results from the activity of living matter, they have insisted 

 that all matter, living and lifeless, results from the activity of mind. 

 They maintain that, were it not for mental activity, there would be 

 no conception, nay not even existence, of those qualities (e.g., sound, 

 colour, force, weight, hardness) of which our non-mental world of 

 matter is composed. 



There is no difficulty in accepting the statement that bile is 

 secreted by the liver ; in this case the product is physical, and it is 

 produced by physiological (i.e., presumably, by chemical and physical) 

 conditions. On the other hand, if we state that consciousness is 

 secreted by the brain, we are linking together two sets of phenomena, 

 the psychical and the physiological, between which a connection is 

 inconceivable. 



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