DUAL CHARACTER OF THE BRAIN. 15 



occur much more frequently in cases of disease of the right 

 side of the brain than in cases of disease of the left side. I 

 have ascertained that both will occur far more frequently in 

 cases of disease of the right side of the brain than in cases of 

 disease of the same extent and the same location in the left side 

 of the brain. Not only disease in the right side of the brain 

 will have the greatest power in this respect, but it will also, if the 

 patient does not die, produce a more marked paralysis ; a more 

 extensive and more permanent one. So that, as regards degree, 

 as regards extent, as regards duration of the paralysis, the right 

 side of the brain is by far worse than the left, showing again 

 that that side has the greater power of nutrition. There are a 

 good many other points showing a difference of the same kind. 

 I pass them over, as time presses. There is, therefore, as you 

 will see, a radical difference between the two sides of the brain. 

 But now this depends, as I have said already, not upon the fact 

 that the two sides of the brain are very different originally, but 

 it depends on development. Every organ which is put in use 

 for a certain function becomes developed, and more efficient in 

 performing that function. Indeed, the organ shows it in size. 

 The left side of the brain, which is used most in our system, is 

 larger than the right side of the brain. The left side besides re- 

 ceives a great deal more blood than the right side of the brain, 

 because it has a preponderance in our system, and every organ 

 that acts much, receives more blood. As regards the influence 

 of action on the brain, there is a fact which hatters know very 

 well. If a person is accustomed for many, many years from 

 adult life — say from 20 up to 40 or more — to go to the same 

 hatter, the hatter will find after a time that he has to enlarge 

 the hat of his customer; and, indeed, a person advanced in life, 

 even having passed, as your lecturer has, 56, has a chance to 

 observe such a change. There is no period of six months that 

 has passed that I have not found that m}'^ hat, if neglected and 

 put aside, became too small. The head, therefore, growing, is a 



