BREAKING AND HANDLING. 269 



important physiological dependencies, or it is a dependency 

 itself which greatly modifies or extends its powers under 

 certain circumstances, which is simply the material phase of 

 mind this is in no wise concerned with the question whether 

 mind is material or otherwise. 



Prof. Bain, in his Mental Science, says, " The brain is the 

 principal, although not the sole organ of mind; and its lead- 

 ing functions are mental. The proofs of this position are 

 these: 



"(i.) The physical pain of excessive mental excitement 

 is localized in the head. In extreme muscular fatigue, pain 

 is felt in the muscles; irritation of the lungs is referred to 

 the chest, indigestion to the stomach; and when mental ex- 

 ercise brings acute irritation, the local seat is the head. 



"(2.) Injury or disease of the brain affects the mental 

 powers. A blow on the head destroys consciousness; phys- 

 ical alterations of the nervous substance (as seen after 

 death) are connected with loss of speech, loss of memory, 

 insanity, or some other mental deprivation or derangement. 



" (3.) The products of nervous waste are more abundant 

 after mental excitement. These products, eliminated mainly 

 by the kidneys, are the alkaline phosphates, combined in 

 the triple phosphates of ammonia and magnesia. Phos- 

 phorus is a characteristic ingredient of the nervous sub- 

 stance. 



" (4.) There is a general connection between size of brain 

 and mental energy. In the animal series, intelligence in- 

 creases with the development of the brain. The human 

 brain greatly exceeds the animal brain; and the most 

 advanced races of men have the largest brains. Men dis- 

 tinguished for mental force have, as a general rule, brains 

 of an unusual size. The average weight of the brain is 

 48 ounces. The brain of Cuvier weighed 64 ounces. Idiots 

 commonly have small brains. 



