462 Edward Livingston Youmans. 



marks, "the brain not only receives impressions uncon- 

 sciously, registers impressions without the co-operation of 

 consciousness, elaborates material unconsciously, calls 

 latent residua again into activity, without consciousness, 

 but it responds also as an organ of organic life to the in- 

 ternal stimuli, which it receives unconsciously from other 

 organs of the body." * 



Science now teaches that we know nothing of mental 

 action, except through nervous action, without which 

 there is neither thought, recollection, nor reason. An 

 eminent authority upon this subject, Dr. Bucknill, says : 

 " The activity of the vesicular neurine of the brain is 

 the occasion of all these capabilities. The little cells 

 are the agents of all that is called mind, of all our sen- 

 sations, thoughts, and desires ; and the growth and reno- 

 vation of these cells are the most ultimate conditions of 

 mind with which we are acquainted." And again ; " Not 

 a thrill of sensation can occur, not a flashing thought, or a 

 passing feeling can take place without a change in the liv- 

 ing organism, much less can diseased sensation, thought, 

 or feeling occur without such changes." 



These facts sufficiently disclose the agency of the bodily 

 system in carrying on mental action ; but the view becomes 

 still more impressive when we observe to what an extent 

 corporeal conditions influence and determine intellectual 

 states. 



The weight of the human brain ranges from sixty-four 

 ounces to twenty ounces, and, other things being equal, the 

 scale of intellectual power is held to correspond with its 

 mass. Cerebral action has thus an enormous range of limita- 

 tion, due to the variable volume of the mental organ, but 

 it is also modified in numerous ways and numberless degrees 

 by accompanying physiological conditions. The brain is an 



* The Physiology and Pathology of Mind, by Dr. Maudsley, p. 20. 



