MENTAL PHYSIOLOGY. 713 



adduced by Dr. Carpenter of this mental phenomenon are varied and 

 exceedingly interesting, but we suppose that no reader of these pages 

 will have any difficulty in referring such experience to himself. But, 

 affirming the facts, will he also agree with the explanation that this 

 power, of seeing old thoughts in a new light, is due to work which the 

 brain has been doing in the mean time, while he was unconscious of its 

 activities ? The brain has been doing work, no doubt. It has been 

 replenishing its forces by rest and nutrition. But has it been j^erform- 

 ing acts of memory and ratiocination ? Has it been sifting aAvay the 

 chaff of irrelevant material, and retaining the grain of reason, and 

 the possessor of the brain all the while unconscious of these mental 

 activities ? If so. Dr. Carpenter's theory of unconscious cerebration 

 is a new, original, and most important light on the nature of mental 

 activities. But if the power of looking at things anew, of considering 

 arguments afresh, giving irrelevances the chance of being forgotten, 

 and essentials the opportunity of being duly weigiied, if this results 

 in the better and clearer understanding of the subject of thought from 

 the simple fact that the mere effi)rt of thought is made under great 

 advantage over the old, then the theory would seem to be unnecessary 

 and superfluous. We think of fishing to-morrow, and pull out fly-books 

 and materials, and are entangled in a medley of feathers, silks, and 

 lines. In the morning we put up our rod, and, with a cast of flies suited 

 to the weather, we seek the stream. Was the mind all night, being 

 unconscious, arranging that which bothered us so in the evening ? So 

 with the materials of ratiocination ; we begin by collecting from all 

 sides that which may be needful, and the mind becomes perplexed and 

 confused, imtil the time for decisive thought or action comes, and then 

 we take those things only which are needful. 



Dr. Carpenter's theory of unconscious cerebration is in accordance 

 with what we may call his regional physiology of the brain. He 

 places the higher psychical functions in the convolutions of the cere- 

 brum, but the cerebral ganglia or the sensorium is the seat of our con- 

 sciousness of these functions, as it is that of external sensations, but 

 of that class of " truly subjective sensations " which comes to the sen- 

 sorium, " the result of changes in that cortical layer of the cerebrum 

 which we have reason to regard as the seat of the higher psychical 

 operations." When the psychical operations of the cerebrum have 

 been reflected downward upon the sensorium, they become subjective 

 sensations, and give rise to the formation of an idea. 



" It is the sensorimn, not the cerebrum, with which the will is in most direct 

 relation; and in order that this doctrine (which lies at the basis of the whole 

 inquiry as to the relation of the will to motives, and the mode in which it deter- 

 mines our character and actions) may be rightly apprehended, it is necessary 

 here to consider the following physiological question : Whether cerebral changes 

 are in themselves attended with consciousness, or whether we only become con- 

 scious of cerebral changes as states of ideation, emotion, etc., through the in- 



