Chap, x.] OF THOUGHT. 441 



that in exciting by electricity this or that region of the grey 

 cerebral cortex of animals, a contraction of this or that group of 

 muscles is caused ; that we can at will make the eyes, the tongue, 

 (fee, move. Mr. Robert Batholon, Professor in the Medical 

 College of Ohio, has obtained the same results by experimenting 

 upon a man whose brain was laid bare by a large loss of osseous 

 substance. Professor SchiS himself has seen that in animals 

 the cerebral substance grew heated in such or such a locality 

 according as it was agitated by such or such a category of 

 sensorial excitations.-' We may compare this nervous mechanism 

 to a piano, the sensitive peripheric fibres being the key-board, 

 the isolated centres of the optic layers the hammers, and the 

 various cortical regions the cords. 



A physiological note responds to each touch : here a secretion, 

 there a palpitation, a contraction or a dilatation of capillary 

 vessels ] elsewhere a sensation, such or such a sensation ; 

 somewhere else, by reflex action, such or such a movement. 



The more voluminous the peripheric nervous cords are, the 

 more developed wUl be the nuclei of the optic layers, and the 

 stronger the current of the sensations and impressions, and the 

 more vigorously agitated will be the cortical perceptive centres, 

 the nervous elements which have consciousness of sensations, 

 which weigh them, compare them, register them ; consequently 

 the more difi&cult will be their ponderatory labour. If at the same 

 time these cortical layers' have little surface and depth, in other 

 terms, if the cerebral hemispheres are little developed, the 

 animal or the man will be peculiarly instinctive ; will instantly 

 and blindly obey the actual impression. If, on the contrary, the 

 perceptive centres dominate, then the being will be intelligent, 

 reflective, master of itself. It is by virtue of this law that the 

 inferior vertebrates, in which the nervous 'intracranian vesicles, 

 olfactory, optical, &c., are as voluminous as the cerebral 

 vesicles (anterior brain ; see Figs. 60, 61), have a rudimentary 

 intelligence. 



1 M. Sohiff, Archives de Physiologie, 1870. 



