Memory. 671 



time the habit which tends to constantly reduce the keenness of the sen- 

 sation arising from a habitual stimulus, tends also to increase the ease 

 and rapidity with which the stimulus is followed by motor action, so 

 that under the force of habit, actions tend to become unconsciously au- 

 tomatic. The increase of this tendency, with its hereditary transmis- 

 sion, intensifies automatism into instwct. This process thus tends to 

 reduce the memory function of the cerebral cells, while it builds up that 

 of the ganglions in the lower brain centers and the spinal cord. The 

 more exactly each repetition of an automatic or instinctive action copies 

 the previous ones, the less of consciousness goes with the action, and 

 the slighter the memory of it that remains. The sameness of the mus- 

 cle movements in walking, have rendered them so far automatic in 

 adults, that on a smooth road a man may walk miles in unconsciousness 

 of the steps he takes. 



The cell organs in the cerebrum, like those in the lower centers, are 

 liable to become so drilled by habit that their action becomes practically 

 frictionless, and they are therefore stimulated without arousing con- 

 sciousness. A large proportion of our mental action goes on thus un- 

 consciously, not counting that which makes up the motor stimuli of the 

 unconscious muscular movements. In this action, the cells which are 

 connected with each other directly or indirectly throughout the brain, 

 constantly influence and stimulate each other ; that is, when one is ex- 

 cited, those in certain relationship with it share the excitement. When 

 the excitement is stronger, it extends also to others less intimately re- 

 lated, and so on. 



The effect of the ramifications and intersections of memory tracks in 

 the cerebrum, is seen on many occasions. There are persons who when 

 they attempt to sing some particular air are liable, in the midst of it, to 

 switch off upon another tune. This happens when both airs are writ- 

 ten in the same time and meter, and have a strain common to both in 

 the same relative part of the piece. When this common strain is 

 reached, the unguarded singer (when singing by ear) is turned off, and 

 winds up on another air than that with whicti he commenced. Example: 

 " Capt. Jinks " and " The King of the Cannibal Islands." 



It is curious to observe how the conversation of a company drifts 

 about from one subject to another, one thing "calling up" another ad 

 infinitum. The relationships of the subjects by which they thus call 

 each other up, are often apparently of the most irrelevant kind. The 

 weather we have here to-day reminds one of similar weather he experi- 

 enced once in Palestine or Mexico, and the thought transported to Mex- 

 ico, is suddenly changed from the weather to something else seen in 

 Mexico, a burro* perhaps. The sound of the name recalls to another 



* A diminutive donkey ; pronounced the same as bureau. 



