674 Dynamic Theory. 



when we come to a gap in the memory of a word or a line, we go back 

 to the beginning, and recite again as far as we can, instinctively expect- 

 ing that what we do know will re-arouse that which has escaped us. It 

 is the same in a passage of music, in a tale, in a landscape, in a busi- 

 ness transaction, &c. 



The process of suggestion is being constantly enacted automatically, 

 and ideas are incessantly arousing others with which they are connected. 

 It is upon the intrusion of an active stimulus from the environment that 

 this automatic "train of thought" is disturbed, and attention is concen- 

 trated upon some particular idea and its correlatives. In such case, the 

 external stimulus is itself the first term of a new series of suggestions, 

 which follow each other till the idea required is found, the reaction from 

 which extinguishes the first term and neutralizes the stimulus. It is 

 evident that the new train of stimulating suggestions is as automatic as 

 the first, the on^ difference being the immediate origin of the initial 

 stimulus. Upon first waking in the morning, cerebral activity begins in 

 a helter skelter sort of fashion, the heat of the circulation alone (prob- 

 ably) furnishing by its frictional arrest in the vascular tubes the neces- 

 sary nervous current to stimulate those cells which happen to be the 

 most mobile and susceptible. This mobility and susceptibility depend 

 directly upon the habit of the cells, and inversely upon their fatigue, 

 exhaustion, &c. The effect of the new incoming stimulus, which gives 

 a fixed direction to the flow of ideas, is produced by the flow of this 

 stimulus over the track which has been taken by similar stimuli in the 

 past, and the re-erection of some of the cells which were affected by the 

 former stimulus. This process determines the flow of blood to the spot 

 stimulated, and arouses that degree of sensation we designate as atten- 

 tion. Observe that attention is not the process, nor the cause of it, but 

 only an effect in sensation of the stimulation which causes the increased 

 movement of the blood, and probably of the movement itself. 



The general position of the tracts of the cortex devoted to the differ- 

 ent senses, was pointed out in the last chapter. These tracts are hered- 

 itary, and at birth are of a more or less definite extent and limit. If, 

 in a young dog, the area in connection with the eyes be cut out, the an- 

 imal will never have any conscious impression of things seen, and no 

 sight memories. According to Munk, the first sensations ( of sight ) in 

 the young animal differentiate the cells in the middle of the area; so 

 that, if, after the dog has had some experience, the central part "of the 

 sight area be cut out, the memories of the things he has seen will be 

 totally destro} T ed, and irrecoverable. But the dog will not be blind, he - 

 can begin over again, and his sight differentiations will go on as before, 

 in the margin of cells still left in the sight area, and he may acquire a 

 respectable stock of new sight memories (but, of course, never recover 



