CHAP. IX. MUSCULAB AND SEEVOUS TISSUES. 107 



It may be urged, if nerve force be a polar force, 

 ■how is it possible to conceive that mental acts, that 

 phenomena connected with the mind, should he the 

 result or the manifestation of polar action ? Without 

 entering into the discussion as- to how far mental 

 acts are the result of an action of the brain, or 

 whether it be through the medium of the brain that 

 the mind acts upon the body, or whether mental 

 phenomena are polar phenomena, I nevertheless 

 believe, that the phenomena associated and con- 

 nected with nervous action are confined to, and can 

 only become manifested in, the animal kingdom; 

 and although they may bear a close relation or 

 connection with the action of other polar forces, they 

 will nevertheless form a distinct class, a class sui 

 generis, and perhaps the highest form by which polar 

 phenomena can become manifested. 



