DUAL CHARACTER OF THE BRAIN. 5 



As regards the faculty of speech, the fact that we have two 

 brains perfectly distinct, one from the other, is not, perhaps, 

 so easily proved as it may be in reference to the mind. We 

 well know, however, that a lesion in the left side of the brain 

 will produce loss of the faculty of speech ; which belongs 

 almost exclusively to the left side of the brain ; but the verj^ 

 fact that the loss of speech depends on a disease in the left side 

 of the brain is itself an evidence that the left side of the brain 

 is quite distinct from the right side ; that it is in fact a brain 

 in itself as regards that particular function of the organ which 

 we call the brain. Therefore, the well-known fact, that out of 

 one hundred cases in which the loss of the faculty of speech 

 had occurred, there is only one in which the disease was to be 

 found in the right side of the brain, is extremely important in 

 showing that the two sides of the brain may act independently 

 of each other. I shall have to return to this again, as much 

 of my argument depends on this point. 



As regards sight, a theory has been advanced by a celebrated 



philosopher, Dr. Wollaston, of London, which has been adopted 



by a great many physiologists, although by no one without some 



hesitation. But as there was no better theory proposed, it 



was received as being at least probable if not demonstrated. 



Wollaston held the opinion that the right side of the base of 



the brain is the centre for sight in the right half of each eye. 



The right half of the right eye is, of course, the half farthest 



from the nose, and the right half of the left eye is the one 



nearest the nose. The inner half of the left eye and the outer 



half of the right eye have for their centre, according to this 



view, the right side of the brain, and, vice versa, the left side 



of the brain would be the centre for sight in the left or outer 



half of the left eye and the inner half of the right e3'e. There 



is, therefore, according to that view, a condition which is quite 



peculiar. If we admit it for a moment, then we ought to find 



that a disease in the left of the brain at the base must destroy 

 34 



