16 THE TONER LECTURES. 



very strong proof that the brain also grows. Action, therefore, 

 is a means of increasing size, is a means of development ; and 

 I have no doubt that a good many among 3^ou have observed 

 that, after they have paid great attention to a subject, they have 

 not only acquired knowledge on that subject, but become much 

 more able to solve questions relating to that subject — that they 

 have developed the part of the brain which has been used for 

 the acts in which they have been engaged, and that part has 

 become far more able to perform its functions. This is perfectly 

 well shown by everything in our system. We well know what 

 a power a pianist can have, if he continues to exercise his fingers 

 and brain on the piano. But such a pianist neglecting to per- 

 form the acts that he was accustomed to perform before, it is 

 very soon found that there is a defect. We must go on, there- 

 fore, exercising the organs in which we desire to have the great 

 activity of life. There is no doubt, therefore, that the left side 

 of the brain, as is shown by its great enlargement compared 

 with the right side, and as is shown also by the quantity of 

 blood that it receives, that that organ is the one which is pre- 

 dominant in our system. But our being right-handed shows 

 this also. 



It is quite certain that right-handedness depends something 

 on nature. As you well know, the wildest populations in the 

 world are right-handed, as we are. There is no people any- 

 where in the world that has not been found right-handed. 

 There is therefore in man a cause which makes the right side 

 of the body to be selected as the one to be used the most, and 

 together with that right side of the body the left side of the 

 brain, which usually moves that right side, is increased con- 

 siderably in power and in size. There is, therefore, primitively, 

 a development given through some natural cause to the left 

 side. We find tliat individuals who are left-handed make use 

 of the right side of the brain, and when they become confused — 

 when they lose, the faculty of expressing ideas by speech — it is 



