1118 PSYCHICAL PROCESSES IN THE CORTEX. [BOOK in. 



character of the animal, converting for instance a vicious, morose 

 dog into a mild and inoffensive one ; and removal of the front 

 parts of the hemisphere seems to have frequently a marked 

 effect in rendering the animal more impressionable and excitable ; 

 he becomes much more demonstrative and 'gushing' in his 

 behaviour than before. But these are mere hints, and the 

 clinical histories of disease in man do not enable us to say 

 much more. Such knowledge as we do possess rather tends to 

 shew that the psychical processes in proportion as they become 

 more complex involve a greater number of nervous factors, and 

 therefore have for their material basis a greater width of nervous 

 area, or in other words their localisation becomes less definite. 

 Thus while we may localize the beginning of a psychical process, 

 a visual sensation for instance, and one of its terminal acts such 

 as the issue of impulses along the pyramidal tract, we cannot put 

 our finger on the seat of the intermediate transactions. These 

 even in the simplest processes must be complex, and must involve 

 many factors. Our simplest conceptions of the external world are 

 based on a combination of visual sensations and tactile sensations. 

 It being granted that the visual sensation, in one phase of its 

 development, is connected with certain changes in some spot of 

 the occipital cortex, there must be some tie between this and 

 the corresponding nervous seat of the tactile sensation wherever 

 that may be, and further ties between these and other parts of 

 the cortex. Hence as we said the psychical process is a function 

 of connections. 



Many of these ties are most probably furnished by the 

 association fibres passing from one part of the cortex to a 

 neighbouring part. We must also probably admit that impulses 

 or to use a more general word, processes, may travel laterally 

 along the tangle of the cortical grey matter, for this, like the 

 grey matter of the spinal cord, seems to form a physiological 

 continuity, no more broken by the fissures than is the cord by 

 its segmental arrangement; and we know nothing as to the 

 limits which must be placed on the distance to which such 

 processes may travel from their focus of origin. Further, seeing 

 how completely in the dark we are as to the reason why we 

 possess two hemispheres, and especially seeing that, as shewn 

 by speech, the whole of each hemisphere is not identical in 

 action with the whole of the other, AVC may perhaps suppose 

 that the fibres of the corpus callosum, which form so large a 

 part of the central white matter of the hemisphere, have other 

 duties than that of merely keeping the points of one hemisphere 

 in touch with the corresponding points of the other hemisphere. 

 But, when we have made every allowance for all these direct 

 intercortical connections, we are driven to the conclusion that 

 the indirect ties between one part of the cortex and another 

 through the lower parts of the brain are of no less, perhaps of 



