commonly said that speech may exist without voice, as in whispering. This is only true, however, if the title of voice be restricted to the sound produced by the vibration of the vocal chords; for, in whispering, there is a sort of voice produced by the vibration of the muscular walls of the lips which thus replace the vocal chords. A whisper is, in fact, a very low whistle.

The modulation of the voice into speech is effected by changing the form of the cavity of the mouth and nose, by the action of the muscles which move the walls of those parts.

Thus, if the pure vowel sounds

E (as in he),
O (as in or),

A (as in hay),

Ơ (as in oh),

A' (as in ah), 00 (as in cool),

are pronounced successively, it will be found that they may be all formed out of the sound produced by a continuous expiration, the mouth being kept open, but the form of its aperture, and the extent to which the lips are thrust out or drawn in so as to lengthen or shorten the distance of the orifice from the larynx, being changed for each vowel. It will be narrowest, with the lips most drawn back, in E, widest in A', and roundest, with the lips most protruded, in 00.

Certain consonants also may be pronounced without interrupting the current of expired air, by modification of the form of the throat and mouth.

Thus the aspirate, H, is the result of a little extra expiratory force—a sort of incipient cough. S and Z, Sh and (as in jugular=G soft, as in gentry), Th, L, R, F, V, may likewise all be produced by continuous currents of air forced through the mouth, the shape of the cavity of which is peculiarly modified by the tongue and lips.

27. All the vocal sounds hitherto noted so far resemble one another, that their production does not involve the stoppage of the current of air which traverses either of the modulating passages.

But the sounds of M and N can only be formed by blocking the current of air which passes through the mouth, while free passage is left through the nose. For

M, the mouth is shut by the lips; for N, by the application of the tongue to the palate.

28. The other consonantal sounds of the English language are produced by shutting the passage through both nose and mouth; and, as it were, forcing the expiratory vocal current through the obstacle furnished by the latter, the character of which obstacle gives each consonant its peculiarity. Thus, in producing the consonants B and P, the mouth is shut by the lips, which are then forced open in this explosive manner. In 7 and D, the mouth passage is suddenly barred by the application of the point of the tongue to the teeth, or to the front part of the palate; while in K and G (hard, as in go) the middle and back of the tongue are similarly forced against the back part of the palate.

29. An artificial larynx may be constructed by properly adjusting elastic bands, which take the place of the vocal chords; and, when a current of air is forced through these, due regulation of the tension of the bands will give rise to all the notes of the human voice. As each vowel and consonantal sound is produced by the modification of the length and form of the cavities, which lie over the natural larynx, so, by placing over the artificial larynx chambers to which any requisite shape can be given, the various letters may be sounded. It is by attending to these facts and principles that various speaking machines have been constructed.

30. Although the tongue is credited with the responsibility of speech, as the "unruly member," and undoubtedly takes a very important share in its production, it is not absolutely indispensable. Hence, the apparently fabulous stories of people who have been enabled to speak, after their tongues had been cut out by the cruelty of a tyrant, or persecutor, may be quite true.

Some years ago I had the opportunity of examining a person, whom I will call Mr. R., whose tongue had been removed as completely as a skilful surgeon could perform the operation. When the mouth was widely opened, the truncated face of the stump of the tongue, apparently covered with new mucous membrane, was to be seen, occupying a position as far back as the level of the an terior pillars of the fauces. The dorsum of the tongue

was visible with diffculty; but I believe I could discern some of the circumvallate papillæ upon it. None of these were visible upon the amputated part of the tongue, which had been preserved in spirit; and which, so far as I could judge, was about 2 inches long.

When his mouth was open, Mr. R. could advance his tongue no further than the position in which I saw it; but he informed me that, when his mouth was shut, the stump of the tongue could be brought much more forward.

Mr. R.'s conversation was perfectly intelligible; and such words as think, the, cow, kill, were well and clearly pronounced. But tin became fin; tack, fack or pack; toll, pool; dog, thog; dine, vine; dew, thew; cat, catf; mad, madf; goose, gooth; big, pig, bich, pich, with a guttural ch.

In fact, only the pronunciation of those letters the formation of which requires the use of the tongue was affected; and, of these, only the two which involve the employment of its tip were absolutely beyond Mr. R.'s power. He converted all t's, and d's into ƒ's, p's, v's, or th's. Th was fairly given in all cases; s and sh, i and r, with more or less of a lisp. Initial g's and k's were good; but final g's were all more or less guttural. · In the former case, the imperfect stoppage of the current of air by the root of the tongue was of no moment, as the sound ran on into that of the following vowel; while, when the letter was terminal, the defect at once became apparent.

LESSON VIII.

SENSATIONS AND SENSORY ORGANS.

1. THE agent by which all the motor organs (except the cilia) described in the preceding Lesson are set at work, is muscular fibre. But, in the living body, muscular fibre is, as a rule, made to contract by a change (Lesson V. §31) which takes place in the motor or efferent nerve, which is distributed to it. This change again is generally effected by the activity of the central nervous organ, with which the motor nerve is connected. The central organ is thrown into activity, directly or indirectly, by the influence of changes which take place in nerves, called sensory or afferent, which are connected, on the one hand, with the central organ, and, on the other hand, with some other part of the body. Finally, the alteration of the afferent nerve is itself produced by changes in the condition of the part of the body with which it is connected; which changes usually result from external impressions.

2. Sometimes the central organ enters into a state of activity without our being able to trace that activity to any direct influence of changes in afferent nerves; the activity seems to take origin in the central organ, and the movements to which it gives rise are called 'spontaneous,' or 'voluntary.' Putting these cases on one side, it may be stated that a movement of the body, or of a part of it, is to be regarded as the effect of an influence

(technically termed a stimulus or irritation) applied directly, or indirectly, to the ends of afferent nerves, and giving rise to a modification of the condition of the particles or molecules which form the substance of the nerve fibres, i.e. to a molecular change, which is propagated from molecule to molecule along the fibres to the central nervous organ with which these are connected. The molecular activity of the afferent nerve sets up changes of a like order in the fibres and cells of the central organ; from these the disturbance is transmitted along the motor nerves, which pass from the central organ to certain muscles. And, when the disturbance in the molecular condition of the efferent nerves reaches the endings of those nerves in muscular fibres, a similar disturbance is communicated to the substance of the muscular fibres, whereby, in addition to the production of certain other phenomena to some of which reference has already been made (Lesson V. § 31), the particles of the muscular substance are made to take up a new position, so that each fibre shortens and becomes thicker.

3. Such a series of molecular changes as that just described is called a reflex action: the disturbance in the afferent nerves caused by the irritation being as it were reflected back, along the efferent nerves, to the muscles. But the name is not a good one, since it seems to imply that the molecular changes in the afferent nerve, the central organ, and the efferent nerve are all alike, and differ only in direction; whereas there is reason to think that they differ in many ways.

A reflex action may take place without our knowing anything about it, and hundreds of such actions are continually going on in our bodies without our being aware of them. But it very frequently happens that we learn that something is going on, when a stimulus affects our afferent nerves, by having what we call a feeling or sensation. We class sensations along with emotions, and volitions, and thoughts, under the common head of states of consciousness. But what consciousness

is, we know not; and how it is that anything so remarkable as a state of consciousness comes about as the result of irritating nervous tissue, is just as unaccountable as any other ultimate fact of nature.