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K. S. LASHLEY 



occipital pole of the cortex. This is not at all in accord with 

 current views concerning the mechanism of habit-formation. 

 Von Bechterew ('11, p. 2020) has summarized the more com- 

 monly accepted view in these words: 



Since from earlier observations in my laboratory (Dr. Protopopov) 

 it appeared clearly that in the production of the association reflex the 

 motor reaction is mediated through the motor cortex and the percep- 

 tion of the associated stimulus occurs in the cortical perceptual or so- 

 called sensory centers (at least for sound, light, and contact) whose 

 localization is now well known, it follows that the excitation of the 

 motor reactions is induced by association fibers which must connect 

 these perceptual or sensory centers with the motor area. 



TABLES 



The percentage of errors made by animals tested for retention of the habit of bright- 

 ness discrimination before and after cerebral operation 





This interpretation, derived largely from data on the dog and 

 man, does not hold good for the rat. In it, at least in visual 

 habit, long transcortical connections are not formed. The same 

 area which functions as a sensory projection area seems to con- 

 tain also corresponding motor fibers. A discussion of the bear- 

 ing of this result upon the condition in higher animals will be left 

 until one additional line of evidence upon the vicarious func- 

 tioning of the cerebrum has been presented (section VI). 



Is the loss of the habit an indication of a general " psychic 

 blindness" or is it due only to the interruption of specific reflex 

 arcs involved in the habit? As far as could be determined the 



