: M, I'll 1 ) 



129 



ANIMAL PHYSIOLOGY. It", 



Tin: 



A MAN > n !:!! I -hud, win -n asked what bo supposed 



B HMind of it trumpet." Tlio 

 shows how dependent the mi ml is 



up>ii i: . No OHO who could both see and 



of comparing sound wit a light, or tono 

 Jour. 



; i tho si iiMtitionM convoyed to tho brain by the eye- 



ilitltnnt as to be incomparable, 



-. mhlouco botwoen sound and light. They 



obey t] a bo absorbed, reflected, and 



the surface of bodies, an wo have Keen light in; 



and. moreover, it is probable that both consist of rapid vibra- 



ding one another at regular intervals, 



liko tlie enlarging circles which follow one another and break 

 upon tho banks when a stone is thrown into the middle- of a 

 etill pond, and disturbs the glassy surface of the water. 



tho cry of t 



let rut \ 



that, it 



even t<> qnadri 



thU fact ?!. 







ii])' in tho sense I 



i 



liaa waj and 



whence the round comaa, 

 ...'.in. Upon 



iU ttucceu. Tbo ides, of 

 ranch dependant 



mind, and not 1 > 



bha miad whare to expect \\-.- -.. n to male* a 



sound of jnst snch a pit i >ae, a* 



the Bound would have if it came from that quarter, to com- 

 pletely impose on the car of the listener a*> to tbo direction from 

 which it comes. 



But although the car is at fault as regards direction, the 

 accuracy of Homo of its other non wonderful in the 



extreme. It can not<; not only tho likeness and di.7t>rence of 

 musical sounds, but of their harmonies when many are Bounded 

 r, and a fine car will detect an erring note when a 

 thousand instruments aro sounded. Tho recognition of slight 



2 



3 14- 



I. THE HUMAN EAR. II. SECTION SHOWING THE HOLLOW OF THE COCHLEA. III. MALLEUS. IV. INCUS. V. STAPES. 

 Reference to Nos. iu Fig. I. 1, piuna; 2, lobule; 3, tube; 4, tympanic membrane; 5, incus, or anvil; 6, malleus, or hammor; 7, 

 tube; S, semi-circular canals; 9, vestibule; 10, cochlea. I., II., III., and IV. enlarged. 



Though there arc th/jsc points of similarity as to tho essential 

 nature and qualities of light and sound, there are also great 

 differences. Light travels with a rapidity which, for all appre- 

 ciable distances that is, for all earthly objects is instan- 

 taneous ; while sound travels, relatively, very slowly, and, when 

 common air carries it, it goes only 1,093 feet during each second 

 of time. Again, while tho vibrations of light are so rapid that 

 it is impossible to know them to bo vibrations but by reasoning 

 upon its effects, the waves of sound may be often observed by 

 the eye when they are propagated through, or originated from, 

 a solid body, as when we see a cord or glass vessel respond to 

 a musical note, or give out a sound when struck. Sound, too, 

 is the vibration of tho substances themselves which substance 

 we can 'feel, or see, or know by means of other senses while 

 light is supposed to be the vibration of some fluid which is im- 

 ponderable, or, in othor words, has no weight, and of which wo 

 know nothing except by the eye. 



Tho waves of sound, then, being coarser and more liable to 

 interference than tho waves of light, it follows that the ear 

 cannot bo so good an indicator of the direction of sound as tho 

 cyo is of the direction of a luminous object. Indeed, the ear 

 au of itself scarcely give us any idea of direction. If tho sound 

 bo short and sharp, like the piercing shriek of tho bat, or even 



70L. I. 



differences is truly wonderful when we consider that not only 

 can tho car know when tho same note is sounded by instruments 

 of different kinds (though physicists are unable to tell us how- 

 there can be any difference, the number of vibrations in a second 

 being the same, and tho medium identical), but very slight 

 differences in the same kind of instruments, such as whether 

 there is one per cent, more or less of a metal in an alloy of 

 which an organ-pipe is made, or of which a bell is cast, are ob- 

 served so shrewdly, that these matters have to bo attended to 

 with tho nicest care. A violin must not only be of a certain 

 shape, but the wood of which it is composed must be of a certain 

 age, to produce the best instrument ; and these observed dif- 

 ferences are carried to such a nicety that fiddles made in a 

 certain part of Germany, in a certain year, are considered the 

 best, and will command almost fabulous sums. Yet all this 

 depends upon what is called timbrt, a word which gives a namo 

 to a something which is entirely dependent on the delicacy of 

 our sense of hearing, but which has not received any other 

 explanation. 



Though we cannot directly connect these niceties of sense 

 with tho intricacies of complication in the organ of hearing, 

 these latter will be seen to be so numerous and peculiar when 

 we describe the ear, that one is not surprised that much 



