DOUBLE TRAINS OF THOUGHT. 329 



the one, perhaps, being a faint greenish gray, while the other is of a yel- 

 lowish white, the proper color given to it by the candle or lamp Tby which 

 it is seen. 



In this feature of double construction the brain itself participates, pre- 

 senting a right and left half approaching one another in form, without 

 being absolutely identical. Much, therefore, of what has been said re- 

 specting the mutual relations of the right and left eye, and the right and 

 left ear, must apply to the right and left hemispheres of the brain ; and 

 it is under this point of view that Dr. Wigan has regarded it in Indc endent 

 his work on the Duality of the Mind. Nor can there be any action of each 

 doubt that each hemisphere is a distinct organ, having the hemis P here - 

 power of carrying on its functions independently of its fellow; that, though 

 each can thus act separately, both can act simultaneously ; and, judg- 

 ing from the cases that have just been presented, it would seem that we 

 are justified in inferring that the common action of the two hemispheres 

 is not for the purpose of a heightening of effect, but only for greater pre- 

 cision, and that in the same manner as it is a rare thing to find two eyes 

 or two ears of equal goodness, so also it is unusual to have two hemi- 

 spheres which are precisely alike. The defects of the one may i nsubor <ji na - 

 be compensated by the superiorities of the other, and thus tion of one 

 a mean result be attained ; and as one eye or one ear can, 

 under the proper circumstances, overpower its fellow, so likewise can one 

 hemisphere of the brain, except in certain cases, which have been some- 

 what imaginatively described as insubordination of one of the hemi- 

 spheres, when insanity is the result, the healthy half being unable to 

 control the diseased one ; and for this reason, we often observe of the 

 insane that they have synchronously, or, at all events, in a very rapid al- 

 ternation, two distinct trains of thought, and, consequently, Double train of 

 two distinct utterances, each of which may, so to speak, be thou s ht - 

 perfectly continuous and even sane by itself, but the incongruities that 

 arise from the mingling of the two betray the condition of such persons. 

 In fhis case doubleness of action is seen in its most exaggerated aspect, 

 but in a less degree, it may be remarked, in the thinking operations of 

 those whose minds are perfectly sound. Thus there is no student but 

 must have observed, when busily engaged in reading, that his mind will 

 wander off to other things, though he may mechanically cast his eyes 

 over page after page ; and the same may occur in listening to a lecture 

 or sermon. But, though the insane man may indulge in two synchro- 

 nous trains of thought, he never indulges in three, for the simple reason 

 that he has not three hemispheres to do it with, the same remark apply- 

 ing to the sane man in the accidental wanderings of his thoughts. 



The overcoming of this insubordination of one of the hemispheres may, 

 to a very considerable degree, be accomplished by education, of which 



