684 Dynamic Theory. 



selves. We early find out that table is a word associated with a certain 

 article. The sound of the word is the audible expression of that thing, 

 just as the light reflected from it is its visible expression, and hearing 

 the word revives the impression of the article with which the word was 

 connected when we first learned it. So the table may stamp itself on 

 the brain in the several ways of light waves, indicating its form and 

 substance ; vibrations from touch, vibrations of the olfactory nerves, if, 

 for instance, it be freshly varnished, &c. , vibrations from sound, got by 

 knocking, &c. Then, by the representative sound of the articulated 

 name table, and by the written or visible representative of the name, 

 the image produced by the direct modes of motion from the table itself 

 is reproduced by the sound waves of the pronounced name, or the light 

 waves from the written or printed name. Now, it seems all these vari- 

 ous modes of motion, conveying impressions of the same thing, make 

 their impressions and differentiations in different parts of the brain. 

 While, therefore, it must frequently happen that a single incoming stim- 

 ulus is able to arouse several distinct, and perhaps widely separated, re- 

 ceptive organs, so it must often likewise happen that the co-operation 

 of several intermedial organs is essential to the proper performance of 

 a motor function. This we have seen to be the case in speech; hearing 

 memories and the memories of the motor action of tongue, lips and 

 jaws, being involved, as well as the memories of the subject we are 

 speaking about. If we are reading aloud, the memory of the forms of 

 printed words, and the memory of the muscular movements of the eyes, 

 must co-operate with those mentioned. If we accompany the perform- 

 ance with gestures, the memory of the muscle movements of the hands, 

 head and back co-operate. After such actions have been performed a 

 number of times, a large proportion of those going to make up one defi- 

 nite series become unconsciously automatic. Thus, the person reading 

 aloud may pay little or no attention to his gestures, or the intonations 

 of his voice, which nevertheless automatically execute themselves while 

 his attention and consciousness are almost exclusively occupied with the 

 sense of what he reads. It is obvious, therefore, that in such case the 

 organs of the motor actions involved have become connected, through 

 previous habit, with each other, so that when the exercise of reading is 

 initiated, the stimulus which wa directed to it by the will, flows from 

 one to another, and causes all the parts concerned to act together. Ob- 

 serve they So not do this at first; the process has to be learned, and the 

 differentiation of the organs, and their attitude of co-operation with 

 each other has to be established by habit. Habit, then, in cerebral ac- 

 tion, as in all other organic action, tends to the establishment and differ- 

 entiation of organs. These are composed of cortical cells, which, when 

 exposed to the appropriate stimulus, move in a definite manner, and set 



