Human Physiology. 



skull, and receives vibrations through the air in the inner cham- 

 ber, through the small bones, and through the bone of the skull. 

 The semicircular canals, placed in three directions, are supposed 

 to show us the direction of sounds, and the nerves of the spiral 

 cochlea the pitch, of which we can distinguish, from the lowest 

 note of the organ to the sharpest insect tone, nine octaves; but 

 there must be sounds on either side beyond the reach of out 

 sense of hearing. 



And what a vast variety of sounds the ear transmits to the 

 mind ; for the quality of tones is as various as the pitch. No- 

 two voices, no two instruments are alike. Violins so vary 

 in quality, roundness, sweetness, loudness, or softness of tone 

 that one may be worth a thousand pounds and another a few 

 shillings. There are voices which bring large fortunes to their 

 possessors ; but all depends upon the power of the human ear 

 to convey, and the human mind to feel, these differences. We 

 cannot conceive of the nature of the differences in the vibra- 

 tions which can make these varying qualities of sound. The 

 waves or impulses may vary in size, or nearness, or intensity, 

 but what can give all the varieties we hear in the notes of birds, 

 the cries of animals, the instruments of an orchestra, or the 

 modulations of the most perfect, wonderful, and delightful of 

 all instruments, the human voice ? 



By our sense of hearing we have warning of danger, we are 

 apprised of the action of the forces of nature, winds, waters, &c., 

 and we know much of what is going on in darkness. We hear 

 in our sleep, for a sudden sound, or the cessation of an accus- 

 tomed one, wakes us; we are guided in darkness, and we hold 

 intercourse with our fellows in language. The blind acquire 

 such use of the sense of hearing that they can tell the distance 

 of a wall, the approach of any one, the nearness of a lamp-post 

 or other obstacle, and a hundred things for which others de- 

 pend upon vision. Hearing, in conveying to the mind a sense 

 of the quality, tones, and modulations of the voice, gives us a 



