384 THE HARMONIES OF NATURE. 



sublime power of speech, which raised their gifted possessors so 

 high above the vulgar crowd, are blotted out at once ; for 

 though death may delay to strike its victim, yet the mental 

 powers are generally laid low for ever, and the object of uni- 

 versal admiration or envy lives but to be pitied. Thus in the 

 brain, both the strength and the weakness of man appear in 

 their fullest light ; and, should his vast superiority over the 

 animal creation, his exalted position as lord of the earth, awaken 

 his pride, the rapidity with which an accident a blow, a con- 

 cussion, the rupture of a bloodvessel may precipitate him 

 from the pinnacle of his intellectual life may well teach him to 

 be humble. 



We know with the utmost certainty that the brain is the seat, 

 the physical or material organ, of our intellectual faculties ; 

 but the internal mechanism of this admirable laboratory of 

 thought and feeling is totally unknown to us. 



We know that from the fishes and reptiles upwards, through 

 the long series of birds and mammalian quadrupeds to man, 

 the brain increases in size and development with the growth of 

 intelligence, but science has not yet been able to sound the 

 depth of its recesses. 



The knife of the anatomist shows us no remarkable difference 

 between the brain of the greatest and of the lowest of mankind ; 

 the chemist finds in every cerebral organ the same substances ; 

 and the microscope sees everywhere the same inextricable 

 labyrinth of delicate fibres and intermingled globules, that unite 

 and separate, and appear and disappear again in a formless 

 mass. In one word, the brain so well conceals its secrets 

 that their discovery seems totally impossible, and man may 

 perhaps sooner be able to fathom the structure of the universe 

 than that of the mysterious instrument of his own thoughts and 

 sensations. 



Inclosed in a shell of solid bone, and thus shielded from many 

 dangers, the brain receives the impressions of the external 

 world, or reacts against them through the agency or channel 

 of the nerves whose delicate filaments, ramifying through 

 the whole body, either transmit its orders or act as faithful 

 messengers of what is going on without. The nerves which 

 communicate external impressions to the brain are called sensi- 

 tive nerves, and of these the optic nerves command the widest 



