556 THE POPULAR SCIENCE MONTHLY. 



be true of the far more complicated operations of the mind of which 

 the higher portion of the brain, the Cerebrum, is the instrument. 

 Now, this Cerebrum we regard as furnishing, so to speak, the mechan- 

 ism of our thoughts. I do not say that the Cerebrum is that which 

 does the whole work of thinking, but it furnishes the mechanism of our 

 thought. It is not the steam-engine that does the work ; the steam- 

 engine is the mere mechanism ; the work is done, as my friend Prof. 

 Roscoe would tell you, by the heat supplied ; and if we go back to 

 the source of that heat, we find it originally in the heat and light of 

 the sun that made the trees grow by which the coal was produced, in 

 which the heat of the sun is stored up, as it were, and which we are 

 now using, I am afraid, in rather wasteful profusion. The steam-en- 

 gine furnishes the mechanism ; the work is done by the force. Now, 

 in the same manner the brain serves as the mechanism of our thought; 

 and it is only in that sense that I speak of the work of the brain. But 

 there can be no question at all that it works of itself, as it were, that 

 it lias an automatic power, just in the same manner as the sensory 

 centres and the spinal cord have automatic power of their own. And 

 that a very large part of our mental activity consists of this automatic 

 action of the brain, according to the mode in which we have trained 

 it to action, I think there can be no doubt whatever. And the illus- 

 tration with which I started in this lecture gives you, I believe, a 

 very good example of it. However, there are other examples which 

 are in some respects still better illustrations of the automatic work that 

 is done by the brain, in the state which is sometimes called Second 

 Consciousness or Somnambulism to which some persons are peculiar- 

 ly subject. I heard only a few weeks ago of an extremely remarkable 

 example of a young man who had overworked himself in studying for 

 an examination, and who had two distinct lives, as it were, in each of 

 which his mind worked quite separately and distinct from the other. 

 One of these states, however the ordinary one is under the control 

 of the will to a much greater extent than the other ; while the second' 

 ary state is purely, I suppose, automatic. There are a great many in- 

 stances on record on very curious mental work, so to speak, done in this 

 automatic condition a state of active dreaming, in fact. For instance, 

 Dr. Abercrombie mentions, in his very useful work on " The Intellectual 

 Powers," an example of a lawyer who had been excessively perplexed 

 about a very complicated question. An opinion was required from him, 

 but the question was one of such difficulty that he felt very uncertain 

 how his opinion should be given. The opinion had to be given on a 

 certain day, and he awoke in the morning of that day with a feeling of 

 great distress. He said to his wife, " I had a dream, and the whole 

 thing in that dream has been clear before my mind, and I would give 

 any thing to recover that train of thought." His wife said to him, 

 u Go and look on your table." She had seen him get up in the night 

 and go to his table and sit down and write. He went to his table, 



