96 Dependence of Mind upon Brain. 



subject of thought is one with which the thinker is 

 not familiar. Mosso, by means of an instrument 

 which he calls a Plethysmograph, has shewn, that 

 during mental action, either in the waking state, or in 

 dreaming, there is a greater amount of blood deter- 

 mined to the brain, and more during difficult than 

 during easy mental action. These are instances of 

 scientific research casting a light upon mental pro- 

 cesses. 



Coexistence of matter and energy is another great 

 truth which appears to be applicable to all nature ; 

 wherever there is matter, there is either active or 

 stored up power ; and as particular forms of energy 

 are in some cases most exhibited by particular kinds 

 of substance, (as magnetism by iron), so mind is 

 associated with living brain. As also we never see 

 the physical powers exhibited except by material 

 substance, so have we never yet observed mental 

 action in a space devoid of material. The most 

 * perfect vacuum yet produced contains many millions 

 ot particles of substance in each cubic inch. Of all 

 the countless number of scientific phenomena observed 

 since men have been able to reliably investigate, not 

 one has afforded us conclusive evidence of mental 

 action entirely independent of these conditions. In 

 accordance also with the usual truth in science, that 

 complicated action requires complex structures; mind, 

 being the most intricate action, is manifested by the 

 most complicated body. 



Mind, like each of the physical forces may be 



