Introduction to the science of language, Volume 1 (of 2)

by A. H. Sayce

Birds possess a superior larynx which differs considerably from that of the mammalia, and has nothing to do with the production of sound. Below this is the inferior larynx at the lower end of the trachea, just before it bifurcates into the two bronchi. This is the organ of voice, and differs a good deal, both in form and structure, in the several species of birds. It is double, except in the parrot and a few other birds, and is almost always symmetrical. It is composed of the lower rings of the trachea united so as to form a tube, at the lower end of which are two protuberances, one in front of the other, and joined together in most birds by a thin rod of bone (the os transversale). To the upper edge of this bone is attached a delicate membrane (the membrana semilunaris), which is turned upwards, and to the lower edge another membrane (the membrana tympaniformis), formed of the membranous wall of the bronchus. The latter membrane is highly developed in singing birds, and still more so in speaking birds, and it can render the first-mentioned membrane (with which it is connected) tense when made to vibrate. In some birds the inferior larynx has as many as five muscles, in others none. It is wanting altogether in vultures. It will be seen that the two membranes correspond to the vocal chords in the mammalia, sounds being produced by the vibration of their margins. The various notes are caused by changes in the degree of tension of the membranes, by differences in the force of the air-current, and by changes in the length and degree of tension of the trachea and other parts. The range of the voice in birds is usually within an octave, but may be much greater.

Serpents have no vocal chords, and their hiss is the result of breath being forcibly driven through a soft glottis. Frogs have no trachea, so that their larynx opens into the bronchial tubes; but the loudness of the croaking of male frogs is due to the distension of two membranous sacs at the sides of the neck. Some frogs have membranous vocal chords: others two reed-like bodies, the anterior ends of which are fixed, while the posterior ends looking into the bronchi are free.

We must wait for the microphone to confute or confirm the statement of M. Langlois, of Freiburg, that ants communicate with one another by means of audible sounds. The recent observations of Sir John Lubbock seem to show the contrary. At all events, the sounds produced by most insects are produced externally and not internally. The stridulation of the cricket or grasshopper is made by rubbing certain file-like organs against the edges of membranous drums on the wings. The pitch of the sounds produced by the cricket is high, consisting of 4,096 vibrations per second. The shriek of the death’s-head moth is produced by the friction of parts connected with the mouth and proboscis, the buzzing of flies and gnats by the rapid vibration of two rudimentary posterior wings called halteres. The humming of humble-bees, beetles, and the like is due to the passage of the air through the spiracles.

Fish, with few exceptions, have no special sonorous apparatus. The noise they make when taken out of the water is caused by the sucking or flapping movements of their mouth or gill coverings. It is possible that the air-bladder opening into the pharynx which is possessed by some fish, may enable them to emit sounds.

Plate I.

Fig. 1. View of the Trachea and Larynx.

Plate II.

Fig. 2. View of the Larynx from above. 1, Crico-arytenoid ligaments; 2, thyroid cartilage; 3, cricoid cartilage; 4, arytenoid cartilages; 5, chordæ vocales; 6, the right thyro-arytenoideus lateralis; 7, the left crico-arytenoideus lateralis (the right being removed); 8, crico-arytenoid ligaments; 9, arytenoideus transversus (connecting the arytenoids); 10, rima glottidis.