320 RESEARCHES ON CORTICAL LOCALISATION AND 



images. Again, the sound of the word " horse " awakens certain 

 sensori-memorial images, which may be of any type, from the 

 written word " horse " to the last horse we have seen. 



The presentation of a sensation, therefore, results in a cerebral 

 process which evolves the psychic product termed a percept. 

 This cerebral process necessarily varies on each occasion on which 

 it occurs. The word " microscope," for example, heard at different 

 times, evokes numerous related but dissimilar sensori-memorial 

 images. 



Perception, therefore, is a cerebral process which is similar in 

 nature but differs in detail on each occasion on which it occurs. 

 It is thus incorrect to speak of a cerebral centre for percepts, 

 which are psychic products that, except by accident, need never 

 be identical even if the arousing sensation is the same. 



It may be remarked that perception can hardly be described as 

 the act of naming objects, for it is as often the reverse, namely, 

 the act of applying one or more sensori-memorial images to a 

 name ; or the identifying of a sensation with a sensori-memorial 

 image. The last corresponds to the crude perceptions of animals : 

 the others to perceptions involving the employment of the symbolic 

 mechanism of language. 



The next grade of complexity of cerebral processes which is 

 rendered possible by the aid of language is the formation of a 

 concept or general notion, e.g. the evolution of a general name 

 such as animal, man, building. The psychic product is termed a 

 concept, and the process of conception involves the revivification 

 of numerous sensori-memorial images which present common 

 points of similarity. 



The cerebral process involved becomes still more complex for 

 the evolution of such " abstract concepts " as heaviness, beauty, 

 religion. 



It is at once evident that the process of conception, whether 

 it takes the form of generalisation from a series of sensori-memorial 

 images to a general name, or of revivification of a series of sensori- 

 memorial images in order that the meaning of a general name may 

 be interpreted, is a very complex one ; and necessarily differs in 

 detail, in spite of a general similarity in nature, on each occasion 

 on which it occurs. It is thus incorrect to speak of a cerebral 

 centre for concepts. 



A physical basis for the several words which symbolise the 



