FUNCTIONS OF THE CEREBRUM. 371 



feeds, as it were, upon the store which has been laid up during the activity 

 of its sensory organs ; but instead of diminishing, like material food, these 

 sensations become more and more vivid, the oftener they are recalled to the 

 mind. 



488. But the operations of the Intellect are immediately founded, not upon 

 Sensations, but upon the Ideas they excite in the Mind.* Some ideas are so 

 simple, and so constantly excited by certain sensations, that we can scarcely 

 do otherwise than attribute them to original or fundamental properties of the 

 mind, called into activity by the sensations in question ; others, however, are 

 of a much more complex nature, and vary according to the peculiar character 

 of the individual mind, the general habits of thought, and its particular condi- 

 tion at the time. In .either case, the formation in the mind of an elementary 

 notion respecting the object of the Sensation, is the first operation in which 

 the Cerebrum can be said to be necessarily concerned, and is introductory to 

 all the rest. The process, whether simple or complex, is termed Perception; 

 and the designation is applied, like Secretion, not merely to the act, but to its 

 result, being used to indicate the notion thus produced, whether it be simple 

 and directly-excited, or more complex and the result of a succession of mental 

 operations. 



489. The difference between Perception and Sensation maybe easily made 

 evident. In order that a sensation should be produced, a conscious state of 

 the mind is all that is required. Its whole attention may be directed towards 

 some other object, and the sensation calls up no new ideas whatever ; yet it 

 will produce some change in the Sensorium, which causes it to be (as it were) 

 registered there for a time, and which may become the object of subsequent 

 attention ; so that, when the mind is directed towards it, that idea or notion 

 of the cause of the sensation is formed, which constitutes a perception. For 

 example, a student, who is directing his thoughts to some object of earnest 

 pursuit, does not receive any intimation of the passage of time, from the 

 striking of a clock in his room. The sensation must be produced, if there 

 be no defect in his nervous system ; but it is not attended to, because the mind 

 is bent upon another object. It may produce so little impression on the mind, 

 as not to recur spontaneously, when the train of thought which previously 

 occupied the mind has been closed, leaving the attention ready to be directed 

 to any other object; or, the impression having been stronger, it may so recur, 

 and at once excite an idea in the mind. Again, the individual may then be 

 able only to say, that he heard the clock strike ; or he may be able to retrace 

 the number of strokes. Now, in either case, a complex perception is formed, 

 without his being aware that any mental operation has intervened. He would 

 say that he remembers hearing the clock strike ; but this would not express 

 the truth. That which he remembers is a certain series of sonorous impres- 

 sions, which was communicated to his mind ; and he recognizes them as the 

 striking of a clock, by a process in which memory and judgment are com- 

 bined, which process may further inform him, that the sounds proceeded 

 from his own particular clock. If he had never heard a clock strike, and the 

 sound produced by it had never been described to him, he would not have 

 been able to form that notion of the object giving rise to the sensation, which, 

 simple as it appears to be at the time, is the result of complex mental opera- 

 tions. But when these operations have been frequently performed, the per- 



Some Metaphysicians have spoken of ideas as transformed sensations ; but this is a gross 

 absurdity. The idea is excited by the sensation, in accordance with the original properties of 

 the mind, and the laws of their operation, just as muscular contraction is excited by the sti- 

 mulus of electricity or innervation; but it would be just as correct to speak of a muscular 

 contraction as transformed electricity or innervation, because excited by either of these stimuli, 

 as it is to call an idea a transformed sensation. 



