752 Dynamic Theory. 



a doorwa} T . Crossing a street was very difficult, and passing an unbuilt 

 space along the street an impossibility. These parties felt as if their 

 will was thwarted and held in possession by some other person. 



We are liable to fall into the same error concerning the original juris- 

 diction of the will in the matter of directing the action of the brain as in 

 the matter of moving the muscles. We talk about concentrating our 

 minds upon a distasteful subject by a powerful effort of the will, &c. 

 We say the will can forcibly ' ' detach attention from the most attractive 

 subjects and direct it to others less attractive." Obviously from what 

 has gone before, the will can do nothing of the sort. Neither can any- 

 thing else do it. 



We are not all made alike, and consequently the effects which the 

 will is competent to produce are different in different people. As a 

 rule, we say the will has power to cause the contraction of the muscles. 

 But in some people this power is of far greater force than in others. 

 We possess some muscles which nobody now has the power to contract, 

 and others which some men can contract and other men cannot. ( See 

 chapter 5. ) We likewise say we have the power to direct our attention 

 in some particular direction; but this power, too, is possessed in very 

 unequal degree by different persons. This is the power to direct the 

 flow of blood to one or another of the cerebral organs, and depends 

 upon the same sort of physiological basis as the concentration of force 

 in muscle action. In fact, the concentration of energy in voluntary 

 muscle action must be preceded by concentration of attention, and this, 

 as the illustrations above cited show, depends upon the intensity of the 

 motives, and their singleness, or freedom from opposing motives. The 

 concentration of attention consists in the singling out of a special ar- 

 terial branch or twig, and stimulating in it an increased supply of 

 blood, by which an increased action is stimulated in the organ, or patch 

 of the cerebral cortex, which depends for its sustenance upon such twig. 

 Such concentration necessarily involves, and to a certain extent depends 

 upon, deprivation of those organs not included in the scope of the 

 stimulation; so that attention includes the increased activity of one or- 

 gan or set of organs, accompanied by. a decreased activity of the others. 



The course by which the nervous stimulus reaches the blood-vessels, 

 appears to be by way of the brain organ itself, which is to receive the 

 benefit. The stimulus, which is primarily a sensation from the environ- 

 ment, reaches its appropriate correspondent organ, and, if strong, sends 

 on from it into its supporting blood-vessels a stimulation which liber- 

 ates a larger supply to the organ. The stimulation of the cerebral or- 

 gan is followed so rapidly by that of the arterial vessels upon which it 

 depends, that their action app%ars simultaneous, though it is doubtless 

 rapidly reciprocal. In those muscular actions which are performed un- 



