CONSCIOUSNESS. 3 



consciousness, by which impressions of past nervous stimuli 

 produce a more or less lasting impression on the brain 

 (or mind). I may point out that ideas are the effects 

 left on the mind by impressions. By being conscious, an 

 animal associates in its mind the idea of pleasure or pain 

 with past impressions ; and, consequently, in the future 

 seeks after impressions which it has learned by experience 

 to be pleasurable, and tries to avoid those which are 

 painful. For example, we may daily note that the young 

 of the higher animals, from experience, gradually increase 

 their ability to obtain and select their food, and to save 

 themselves from their enemies. We see in ourselves how 

 greatly experience in boxing and fencing perfects the 

 automatic movements which are necessary to guard us 

 from hurt by fist or sword-point. The necessary retention 

 of ideas (or memory) appears to be due to a modification of 

 the brain substance by which an impression of an original 

 idea is produced by means of another idea that has been 

 associated with it. Professor Lloyd Morgan aptly com- 

 pares this modification of brain substance to that under- 

 gone by a used phonograph, the cylinder of which has 

 become indented in such a way by the voice, that it is 

 capable of reproducing similar wave-sounds at a subsequent 

 time. Ideas, we must remember, are no more retained 

 in the mind than are sounds in the phonograph. Habits 

 are thus formed in the individual, and by the principle 

 of heredity are transmitted to the offspring as instincts. 

 We may define an instinct as a habit which has become 

 hereditary and automatic, and which can consequently 

 be exercised without teaching, imitation, or experience. 

 Or we might regard instinct, in its collective sense, as 

 hereditary memory. Granting, as we can scarcely help 

 doing, the truth of the principle of evolution, we must 

 admit the existence of mental progress by means of con- 



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