00-., 



UNDI'I. \TU: V KitRi'KS -ACiUSTICS. 



i: or IIIKPI. 



(ohlfinch, the Urk, the linnet, the canary. "J chaffin 

 and to th<e with * monotonoiu cry, like the *wnllo 

 jmiraw, the starling ; but N< N-dly 



disagreeable cry, inch a> 



the nvrii. '1 inplux organ nocaf- 



*ry I. ut also m fine 



gwuenU organuat : 



The windpipe in birds presents * -Jugular 



modification*. As the voice it produced in the inferior 



Urrnx iif bird*, situated at the lower part i.f the wind- 



. this tnU> come* to form, together with the nnmtli, 



r pipe pUced in front of the organ of voice. 



bird* cornea to occupy a place 



. - - .... . , .... .,, . . , . organs of speech 

 hunun Nrly. It is capable of living short. 



br the diminution of tin- spaces ^between tho 

 rings thcmmlvm, hut also by tho rings being received 

 one within the other. In many birds, the windpipe is 

 much longer than the neck, bring thrown into coiirnl i- 



- Thu structure is observed in the cock-of-tho- 

 wood, tho stork, and crane. In the wild swan, the con- 

 r.ilutiniis of tlie windpipe are lodged in a cavity of the 

 breast bone. Nor is the windpi]>e always cylindrical, 

 fur in herons and cormorants it has a conical figm.-, 

 becoming gradually wider and wider towards the month. 

 In some species of ducks it presents a sudden dilatation ; 

 while in the goosander, and some members of the duck 

 family, it undergoes gradual dilatations. 



That the inferior larynx of birds is the true organ of 

 voice has been proved by many experiments. For ex- 

 ample, anatomists have divided the windpipe in singing 

 birds, such as the blackbird, almt the middle of its 



h, so that the air could no longer pass through 

 Mi|-rior larynx, and yet tho bird would continue to 

 though with feebler tones than before. Similar 

 limenta have been made on magpies and on ducks. 

 r such an experiment, tho magpie is found to cry 

 with as great intensity of tone, and with the 



ness, as before the >] oration. Again, if air be 

 M int. i the l.nnichial divisions of a duck, after their 

 ther with the. inferior larynx from the 

 body, a sound exactly similar to the natural cry of tin- 

 bird is obtained. K\cn after the bronchi have been cut 

 away, by Mowing into the trachea the same sound is 

 produced. 



It is not, however, to bo concluded that the superior 

 ):o modifying influence on the voice in 

 most birds. It is manifestly opened and closed rapidly 

 in singing birds, so that it is impossible to doubt that it 

 takes an active part in the production of melody. In 

 the son.,' of the eaiiary and the linnet, its simultaneous 

 miiM mi-lit* with those of the mouth are readily oh 

 nerved. Its effect, however, on the pitch of the voi 



-ud to ex<-. tone. 1'hysiologists still 



doubt whether the Founds of the voice in birds are tho 

 result, an in man, of thu vibrations of a reed or tongue ; 



- in mere tlute pii.es, of the vibrations of a column 



1 by friction against the lips of an opening, 

 i'piestionably a great difference in the mode 

 in which voice is produced in different birds. It seems 

 certain that the simple organ of voice in the duck, the 

 goose, and the like, is a reed instrument. In these tin- 

 rood cords, or bands, which form the exterior margin 

 of the opening of the larynx, can be seen to vibrate 

 tronglj; while the sound produced, closely resembles 

 that arising from the vibrations of membranes, lint it 

 is by no means so clear that the piping and whistling 

 sounds of singing birds are produced in tho same 

 manner; and it is not impossible that these may be 

 effected in the same mode as whistling by the mouth 

 in man, 



d reasons, however, nmv l>o urged in favour of 

 tin- opinion, that the som hints are 



tlie cMWt ot thu vibrations of tongues, as well as t In- 

 voice of th.- duck and the goow. mp!.-, the 

 vocal cord* under n lion e a n 

 being thrown into vibrations; and even though the 

 the air may ). j n j,art , ,,, -enii-d in tin- pro- 

 duction of tho KiuniU, a coiii|>elisation must arise bc- 



thc vibrations of the air and those of the 

 nts. If this be correct, the organ of roiofl in 



would i rely analogous to ., ),. 



pipe; but would, in part, | .s-ess : ;tioii of :l 



ania&t It is found that the length tA 

 windpi]K- has but a lit influence, on the 



produced by the larynx ; and that fact corrt'Nponds with 

 the slight 'lie pitch of the not. I l,y 



placing a tulie in front of the human larynx. It i 

 found, that sounds produced by blowing, by means of a 

 tube inserted in a bronchus, through the lower larynx of 

 some birds after its separation fiom iln- windpipe, are 

 not perceptibly altered in pitch by holding a tul 

 front of the larynx: thus is continued tl 

 of tho lower larynx in birds to the ei. ; the 



larynx in man. It may l>e added, that the gr 

 number of the notes of birds can In 

 inferior larynx by varying tho force of the blast, whii-l., 

 at first sight, seems to jKiint to a resemblance with tho 

 effect of blowing by varying force upon tlie notes of 

 flute-pipes, of the same size as the windpipe of - 

 singing birds. But it is to be remembered, thu: 

 same variations of notes, by varying the s; 

 the blast, may be produced in reed instruments with 

 membranous tongues, and even in reeds with very dcli- 

 H-tallic tongues. 



The influence of the windpipe on the notes, may be 



r the same as that of the notes of flute-pipes. 

 may merely affect them in the manner of the tu: 

 reed instruments. Contraction of tho upper opening of 

 the windpipe, at the superior larynx, may lower tho 

 note, as in pipes and reed instruments. 



An influence may be exerted on the sounds produced 

 in tlie lower lannx liy the tympaniform meml.i 

 which vib: "ig'y at tho time. Between the 



internal vocal cord, tho semi-lunar membrane, and the 

 tympaniform membrane, there, is a relation of 



lion, the latter being analogous to the mcnihiane 

 fni iiu-d of a reed stalk. 



The muscles which vary the tension of the walls of 

 the vocal pipe are in continual action during the modula- 

 tion of the voice, in order to adjust the tube of the 

 windpipe to the pitch of the glottis; but tlie numl > 

 vibrations may l>e determined by the glottis, reinforced 

 by the waUs of the pipe, as in mamn 



The voice of birds, as of other animals, is also in a 

 minor key. The range of notes is commonlv within an 

 octave, though some birds can great! . In the 



parrots, which have a voice of great power, tlie inferior 

 larynx is single. The two in< t flu; h.i\n\ 



leave a narrow chink between them, through which tho 

 air is forced from thu 1 lings. Thou memhiaiies, \ il. rat ing 

 in all their dimensions, produce that harsh ami disje 

 able quality of sound peculiar to them. Tlu-v can also 

 whistle, during which the glottis is probably silent, and 

 the column of air vibrates as in a flute, when a vibr.n 

 mo\ement is communicated by the air traversing thu 



walls of the tube. 1'uside.s the power ,,i sp. 



;sed by some binls, many can imitate almost every 



sound they hear: the blackbird ha-< been known to 



imitate, the sound of the nightingale, the crowing of 



iiinion cock, and tho cackle of the hen. Thu jay 



d to mock th iii. eh and tho 



ing of a horse so closely, that it was scanvly 



belieVM to bo a bird by those who heard it ; it ean aUo 



imitate tho calling of fowls to their loud, and the 



i^' of the house-dog. 



Tho variety in the song of singing birds is a subject 

 of the greatest interest. Thu son; stei ,, properlv so 

 called, include the skylark, tho woudlark, the thrush, 

 tin- blackbird, and the nightingale. A si ..t" 



the mite, ,,i , aeh of th 



The skylark i ur most agreeable son-slurs. 



of trilling and warbling notes variously n 



..inally intei rupted by a powerful whirling. S. 



the lark sings on the ground, perched on a clod, 

 or crouched among the grass; but in com- 



mencing its song, it starts off, ns.-s perpendicularly or 



