384 THE POPULAR SCIENCE MONTHLY. 



expend their influence directly upon muscles, they may, neverthe- 

 theless, be regarded as a part of the motor machinery, since they 

 act on other centers which are motor ; and, by the associated ac- 

 tion of these two kinds of centers, the will gradually acquires a 

 real though limited control over the voluntary muscles. 



Volition, whatever its origin, involves a state of excitation of 

 the brain and stimulation of body and mind. Opposition only 

 serves to increase its energy (as the load in " the nerve-muscle 

 preparation " * augments the force of the contraction), and under 

 excitement intellectual as well as muscular work is more easily 

 done. Emotional excitement, if not of too absorbing a nature, pro- 

 motes intellectual activity, but the latter is itself accompanied by 

 a peculiar exaltation of feeling which is a source of the keenest 

 psychical satisfaction. 



Stimulation, then, either sensory or volitional, is a necessary 

 antecedent of activity — in common parlance, its cause. Prof. 

 Bain advocates the idea that stimulation is the sole cause of pleas- 

 ure, the nutritive functions by keeping up the vital energy en- 

 abling stimulation to be carried to certain lengths before degen- 

 erating into pain. If we fall short of the pain limit, we fail of 

 the satisfactions which flow from the conscious expenditure of 

 energy to the full degree of which the organism is capable. If 

 we exceed this limit, we pay the penalty of physical degeneracy 

 and resulting mental decrepitude with the accompanying falling 

 off of activity, and hence of pleasure. Degeneration also follows 

 from disuse — that is, the neglect of stimulation, and consequent 

 inaction. 



Sir William Hamilton, following Aristotle, defines pleasure as 

 " the reflex of the spontaneous and unimpeded exertion of power 

 of whose energy we are conscious/' But exercise of power occurs 

 as a result of stimulation. The larger statement of Prof. Bain, 

 therefore, includes that of Hamilton ; and, since the spontaneous 

 exertion of power with the accompanying state of consciousness 

 depends on excitation of motor centers, both these statements are 

 involved in my sixth thesis, viz., that movements are the primary 

 source of pleasure and pain which, in the experience school of 

 psychology, are recognized as the basis of the entire mental life. 



Mr. James Ward f regards the reflex movements immediately 

 expressive of pleasure and pain as primordial, the voluntary 

 movements being elaborated out of these. But movements occur 

 presumably below the plane of consciousness — e. g., in vegetable 

 protoplasm. We may therefore conclude that, in the developing 

 animal series, the lowest members of which are indistinguishable 



* The calf-muscle, with its nerves, taken from the leg of a frog. Within certain limits, 

 the heavier the weight attached to the muscle the more powerfully it contracts when the 

 nerve is stimulated. ■(• Loc. cit. 



