LIFE AND MIND 



cial actions and reactions which they display, 

 from instant to instant, in their converse with 

 the special objects, animate and inanimate, amid 

 which they move." ^ 



This last point is one which requires further 

 illustration. Concisely expressed, it amounts to 

 this — that psychology is distinguished by deal- 

 ing in a particular way with the relations be- 

 tween the organism and its environment. A 

 few illustrations will render this perfectly in- 

 telligible — will show us that mere nervous 

 physiology is not, and never can be, psycho- 

 logy. 



Nervous physiology treats of relations sub- 

 sisting within the organism. It explains how 

 waves of molecular motion, set up in a nerve 

 centre and transmitted along a nerve axis, cause 

 contraction in the fibres of a muscle, or secre- 

 tion in a gland, or molecular rearrangement 

 in the substance of the tissues, or set up a 

 new molecular undulation in some other nerve 

 centre. It seeks to formulate the conditions 

 under which nervous stimulation and nervous 

 discharge take place. Or it shows how certain 

 feelings are invariably sequent upon certain re- 

 arrangements of the molecules composing the 

 nerve substance. Even if it recognizes, as it 

 does continually recognize, some force external 

 to the organism, which causes the molecular re- 



^ Spencer, Principles of Psycho logy y vol. i. pp. 137, 138. 

 Ill 



