8 INTRODUCTION. 



that the lower down we go in the animal kingdom, the 

 more we observe reflex action, or non-mental adjustment, 

 to predominate over volitional action, or mental adjust- 

 ment. That is to say, the lower down we go in the 

 animal kingdom, the less capacity do we find for changing 

 adjustive movements in correspondence with changed 

 conditions ; it becomes more and more hopeless to teach 

 animals — that is, to establish associations of ideas; and 

 the reason of this, of course, is that ideas or mental units 

 become fewer and less definite the lower we descend 

 through the structure of mind. 



It is not my object in the present work to enter upon 

 any analysis of the operations of mind, as this will require 

 to be done as fully as possible in my next work. Never- 

 theless, a few words must here be said with regard to the 

 main divisions of mental operation, in order to define 

 closely the meanings which I shall attach to certain terms 

 relating to these divisions, and the use of which I cannot 

 avoid. 



The terms sensation, perception, emotion, and volition 

 need not here be considered. I shall use them in their 

 ordinary psychological significations; and although I 

 shall subsequently have to analyse each of the organic or 

 mental states which they respectively denote, there will 

 be no occasion in the present volume to enter upon this 

 subject. I may, however, point out one general con- 

 sideration to which I shall throughout adhere. Taking 

 it for granted that the external indications of mental 

 processes which we observe in animals are trustworthy, so 

 that we are justified in inferring particular mental states 

 from particular bodily actions, it follows that in con- 

 sistency we must everywhere apply the same criteria. 



For instance, if we find a dog or a monkey exhibiting 

 marked expressions of affection, sympathy, jealousy, rage, 

 &c., few persons are sceptical enough to doubt that the 

 complete analogy which these expressions afford with 



in either case ; but this is the side issue which concerns the general 

 relation of body and mind, and has nothing to do with the guarantee 

 of inferring the presence of mind in particular cases. 



