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ployed, as an extremely inferior imitation, in making artificial instruments resembling the larynx. The upper and free edges of the cords, which are sharp and straight, are the parts thrown into vibration during the production of the voice.

31. With reference to the muscles of the larnyx, we may state beforehand that the principal movements to be effected by them relate to the change of tightness and the change of distance of the two chords, for which purposes opposing pairs are necessary. By one action, the chords are tightened; by another relaxed; by a separate action they are approximated, and by the antagonist of this they are parted asunder.

FIG. 11.*

The great muscle of tension of the cords, the chief and the most powerful of all the muscles of the voice, is the cricothyroid, exhibited in the figure. It is a short, thick triangular muscle, seen on the front of the larynx, situated on the fore part and side of the cricoid cartilage. It arises by a broad origin from the cricoid cartilage, reaching from the median line backwards upon the lateral surface, and its fibres, passing obliquely upwards and outwards, and diverging slightly, are inserted into the lower border of the thyroid cartilage.' The contraction of the two cricothyroid muscles causes the thyroid and cricoid cartilages to turn on each other behind; thus, if we suppose the cricoid cartilage to remain fixed, the upper part of the thyroid is carried for

* A diagram, slightly altered from Willis, showing a bird's-eye view of the interior of the larynx.-1. Opening of the glottis. 2. 2. Arytenoid cartilages. 3. 3. Vocal chords. 4. 4. Posterior crico-arytenoid muscles. 5. Right lateral crico-arytenoid muscle; that of the left side is removed. 6. Arytenoid muscle. 7. Thyro-arytenoid muscle of the left side; that of the right side is removed. 8. Upper border of the thyroid cartilage. 9. 9. Upper border and back of the cricoid cartilage. 13. Posterior crico-arytenoid ligament.'-QUAIN.

ward or away from the other, drawing with it the ends of the vocal chords, which are attached behind to the cricoid cartilages through the arytenoid (see fig. 11). In this way the vocal cords are stretched in proportion as the muscle contracts itself. The counteracting or antagonistic muscles are exhibited in the fig. (7), passing between each arytenoid cartilage and the thyroid, near the extremity of the vocal cords.

For governing the aperture of the glottis, we find a muscle passing between the two arytenoid cartilages (6); by its contraction drawing them together, and thus approximating the cords. The cords are separated, and the glottis widened, by a pair of muscles, exhibited in the figure (4, 4), passing between the arytenoid and cricoid cartilages behind. No. 5 in the figure is another muscle connecting the same two cartilages laterally, and operating to contract the glottis.

32. The Larynx, considered as an instrument for the production of sound.-From the existence of two vibrating strings or cords, the first and obvious supposition, with regard to the Larynx, was to rank it with stringed instruments, such as the violin, where the same string produces a higher or lower note, according to the degree of tightness given to it. But that two strings, about an inch long, should so vary in tension as to give out a range of notes extending to more than two octaves, is altogether unparalleled in the experience of stringed instruments. A more accurate comparison appears to hold with reed instruments, such as the pipe of an organ, where the sound is produced by a vibrating reed. Müller imitated the human voice by stretching two elastic membranes across the mouth of a short tube, each covering a portion of the opening, and having a chink left between them. By prolonging the membranes downward into the tube, so that not merely their edges, but their whole planes, might be thrown into vibration, Mr. Willis carried still farther the imitation of the human Glottis. From experiments on an artificial glottis thus formed, it appeared that various notes could be obtained by altering the tightness of

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the tongues: the more tense they are, the higher is the note produced. 'It is true that a scale of notes, equal in extent to that of the human voice, cannot be obtained from edges of leather; but this scale is much greater in india-rubber than in leather; and the elasticity of them both is so much inferior to that of the vocal ligaments, that we may readily infer that the greater scale of the latter is due to its greater elastic powers.' It is also found that in membranous tongues the increased strength of the blast can somewhat raise the pitch, the tension remaining the same.

I quote the following summary of the action of the voice, from a paper in the Proceedings of the Royal Society (June 19, 1862), by Mr. John Bishop, containing the results of actual inspection of the movements of the vocal cords, with the aid of the Laryngoscope of Czermak :

In ordinary breathing the glottis is wide open, and the arytenoid cartilages are thrown wide apart; but on the production of the most simple sound, these cartilages are suddenly and rapidly closed, and the edges of the vocal cords come into juxtaposition with each other, so as to leave no interval between them in their entire length.

'In the production of the lower tones of the voice, the vocal cords may be seen to vibrate throughout their whole length, and even at their prolongations at the base of the arytenoid cartilages; they seem to vibrate also throughout their entire breadth. As the pitch of the tones rises in the scale, the length of the cords in a state of vibration diminishes, and they are pressed more closely against each other: as the tones become more acute, the pressure is increased, and the tension of the vocal cords augmented; the breadth of the cords is also diminished.

'When the chest tones have arrived at the limit of the scale of acute range, and the falsetto tones commence, the glottis is seen to be more closely pressed together, and the edges only of the vocal cords are suffered to vibrate, as Garcia has already observed. On the other hand, while the chest tones are produced, a larger surface of the vocal cords is in a state of vibration. When the falsetto tones are produced, it appears that the very extreme edge only of the cord vibrates, and a much less expenditure of breath is required. While the highest notes of the voice

are intoned, the vocal cords are so closely pressed together, that a small portion only of the glottis is seen to yield to the pressure, which takes place nearly at its central portion.

'From the inspection of the vocal organs now so easily obtained, it may be stated in general terms that, as the voice ascends from its lowest to its more acute tones, the lengths of the vibrating portions of the vocal cords are proportionally diminished, while at the same time their tensions are increased: and, in fact, they present the same phenomena as those of musical cords, and they appear to obey the same laws, as Ferrein so long since supposed, and which have since been confirmed by Müller and by myself.

'Moreover, the vocal cords form a kind of valve, which is situated in a tube, and acts on the column of air in the manner of a reed.

'It is observed that while the pitch of the tones of the voice becomes more grave, the epiglottis is depressed and the pharynx is relaxed; and, on the contrary, as the pitch becomes more acute, the epiglottis is raised and the pharynx becomes contracted: the depression of the epiglottis probably assists in deepening the pitch of the vocal tube in the same manner as the lid of an organ pipe does.

'In the production and modulation of the voice, it is astonishing with what accuracy some persons are able to produce at will, sounds of a determinate pitch and of a quality which charm and captivate the ear of a musician. The muscles which are principally concerned in this faculty are the thyro-arytenoid and the lateral crico-arytenoid. The crico-thyroid is limited to stretching the vocal ligaments.

'The mere turning of the vocal cords on their axes, out of the vocalizing position, does not afford sufficient space for ordinary breathing, as supposed by Mr. Willis, but we find that the arytenoid cartileges and vocal cords are widely separated during ordinary breathing.

'With regard to the controversy as to whether the vocal organs are to be considered as a stringed instrument or as a reeded pipe, it has been thought by some physiologists that the same organs cannot possibly perform the offices of both. However, under the denomination of reeded pipes, we find a great variety of form and structure, and it is not difficult to conceive that while

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the time of an oscillation of the vocal ligaments obeys the same laws as musical strings, the valve of the glottis in opening and closing the vocal tube performs an action resembling that of some of the musical reeds.

'The human organs of voice have been considered by a great many distinguished philosophers as constituting a reeded instrument, and the relation in which they stand to instruments of that character has been already discussed in my paper in the 'Transactions' of the Royal Society for the year 1846; it only remains to remark that the phenomena brought to light by means of the laryngoscope tend to confirm the idea that the vocal organs really perform the double effect both of reed and string.

'In ejaculatory sounds, such as the production of the syllables há, há, há in laughing, the glottis is opened at each intermission and closed at each intonation of sound, thus producing a rapid succession of opening and closing the glottis.'

The difference between the male and the female voice is due to the size of the larynx and the length of the vocal cords; both which are greater in the male. In persons of the same sex, there are gradations in these particulars.

33. The musical voice depends on the action of the vocal cords, in conjunction with the other parts of the larynx; the cranium also operating as a resounding mass. The articulate voice contains, in addition, the workings of the mouth, tongue, and nostrils. Articulation may involve the musical voice, or the action of the cords; it may, also, be toneless. In a whisper there is no musical sound. We may exert the voice to a considerable degree of loudness, without introducing tones, in which case, the supposition is that the windpipe is made vocal by its rings or other parts, and not by the usual medium of the cords. Such toneless speech involves a great expenditure of power, as well as the propulsion of a great volume of air, and is, for that reason, as well as on other grounds, avoided.

The articulate sounds are commonly divided into vowels and consonants, but the division is not founded on any broad line of demarcation. Certain letters have come to be called vowels, and others to be called consonants.