INTRODUCTORY. 7 



inquiry. (2) Observation of the ingoings and out- 

 comings. It is the latter set of signs that are 

 principally studied in this volume. 



As to the observation of the ingoings and out- 

 comings of the subject observed, the following 

 propositions may be laid down : 



(a) The ingoing quantities of material equal the 

 outcoming quantities of material, plus or minus any 

 change in the quantity of material of the body of 

 the subject. 



(6) The ingoing quantities of force equal the 

 outcoming quantities of force, plus or minus any 

 change in the quantity of force stored in the 

 subject. 



(c) Some force must be ingoing if any change 

 occurs within. 



(d) The difference, or change in kind, between 

 the income and the outcome is due to changes 

 occurring in the organism. 



(e) Conversely, changes occurring in the organism 

 may in part be expressed by describing the differ- 

 ence, or variability in kind, between the income 

 and outcome. 



(/) It follows that we may reasonably observe 

 and describe the difference between the ingoing 

 and outcoming forces, and also observe changes 

 occurring in the material structure of the subject. 



The animus and object of the inquiry described 

 in chap. xix. is to determine, by means of observa- 

 tion and an experimental method, the effects of 

 external circumstances in aiding and producing the 

 physical or material basis of mind. 



