cular verb, or designation, implying action; to taste implies the movement for bringing the substance upon the tongue; to smell, or to snuff, means an active inhalation of the odorous stream; to feel signifies the movement of the hand or other organ over the surface in search of impressions; in like manner, to hear and to see are forms of activity. In the cases of taste and smell, the action does not contribute much to the sensation or the knowledge; in the three others (two especially) it is a material element, since in all of them, direction and distance are essential parts of the information. Now, since movement is required to bring objects within reach, the value of any of our senses will depend very greatly upon the activity of the organs that carry the sensitive surface, the tentacula, so to speak. This activity grows out of the muscular and nervous energy of the frame, and not out of the particular endowment of the sensitive part. It is a voluntary exertion, at first spontaneous purely, always spontaneous in some degree, but linked to, and guided by, the sensibility. The flush of activity lodged in the arm and fingers is the first inspiration towards obtaining impressions of touch; the liking or disliking for the impressions themselves comes in to modify and control the central energy, and to reduce handling to a system.

15. Touch being concerned in innumerable handicraft operations, the improvement of it as a sense enters largely into our useful acquisitions. The graduated application of the force of the hand has to be ruled by touch; as in the potter with his clay, the turner at his lathe, the polisher of stone, wood, or metal, the drawing of the stitch in sewing, baking, taking up measured quantities of material in the hand. In playing on finger instruments, the piano, guitar, organ, &c., the touch must measure the stroke or pressure that will yield a given effect on the ear.

16. The observations made on persons born blind have furnished a means of judging how far touch can substitute sight both in mechanical and in intellectual operations. These observations have shown that there is nothing essential to the highest intellectual processes of science and thought that may not be attained in the absence of sight. The integrity of the

OBJECTS OF HEARING.

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moving apparatus of the frame renders it possible to acquire the fundamental notions of space, magnitude, figure, force, and movement, and through these to comprehend the great leading facts of creation as taught in mathematical, mechanical, or physical science.

17. The skin is liable to feelings not produced by an external pressure, but resembling what would arise from particular actions, and suggesting them to the mind. These are called 'subjective sensations.' The tingling of a limb asleep, formication, or a sensation as of the creeping of insects, heat, chilliness, &c., are examples.—(TODD and BOWMAN, I. 433.)

SENSE OF HEARING.

This sense is more special and local than the foregoing, but agrees with Touch in being a mechanical sense as distinguished from what I have chosen to consider as the chemical senses-Taste and Smell.

1. The objects of hearing, are material bodies in a state of tremor, or vibration, brought on when they are struck, which vibration is communicated to the air of the atmosphere, and is thereby propagated till it reach the hollow of the ear.

All bodies whatever are liable to the state of sonorous vibration; but they differ very much in the degree and kind of it. The metals are the most powerful sources of sounds, as we see in bells; after these come woods, stones, earthy bodies. A hard and elastic texture is the property needed. Liquids and gases sound very little, unless impinged by solids. The howling and rustling of the wind arise from its playing upon the earth's surface as on the Æolian harp. The thunder is an example of a pure aerial sound; the intensity, great as it is, being very small in comparison to the mass of air put in agitation.

It belongs to the science of Acoustics to explain the production and propagation of sound, and the forms of sounding instruments of all kinds. Here we are considering the effects, and not the instruments of sound. Even the human voice, whose description cannot be omitted in a treatise on mind, will come in under another head.

2. The organ is the Ear. It is divisible into three parts; the external ear, the tympanum or middle ear, and the labyrinth or internal ear; and of these the first two are to be considered as accessories or appendages to the third, which is the sentient portion of the organ.'

The external ear includes the pinna-the part of the outer ear which projects from the side of the head, and the meatus or passage which leads thence to the tympanum, and is closed at its inner extremity by the membrane interposed between it and the middle ear (membrana tympani).'

'The tympanum, or drum, the middle chamber of the ear, is a narrow irregular cavity in the substance of the temporal bone, placed between the inner end of the external auditory canal and the labyrinth. It receives the atmospheric air from the pharynx through the Eustachian tube, and contains a chain of small bones, by means of which the vibrations, communicated at the bottom of the external meatus to the membrana tympani, are conveyed across the cavity to the internal ear, the sentient part of the organ. The tympanum contains likewise minute muscles and ligaments which belong to the bones referred to, as well as some nerves which end within this cavity, or only pass through it to other parts.'

As to the cavity of the tympanum, I shall content myself with quoting the description of the anterior and posterior boundaries by which it connects itself with the outer and inner portions of the ear, and which are therefore the main links in the line of communication from without inwards.

The outer boundary, formed by a thin semi-transparent membrane, the membrana tympani, which may be seen by looking into the ear, 'is nearly circular, and is slightly concave on the outer surface. It is inserted into a groove at the end' of the passage of the outer ear, and so obliquely that the membrane inclines towards the anterior and lower part of the canal at an angle of 45°. The handle of one of the small bones of the tympanum, the malleus, descends between the middle and inner layers of the membrane to a little below its centre, and is firmly fixed to it; and as the direction of the

handle of the bone is slightly inwards, the outer surface of the membrane is thereby rendered concave.'

The inner wall of the tympanum, which is formed by the outer surface of the internal ear, is very uneven, presenting several elevations and foramina. The foramina or openings are two in number, the oval foramen (fenestra ovalis) and the round or triangular opening (fenestra rotunda). Both are closed with membranes, which render the inner ear, with its containing liquid, perfectly tight. To one of them, the oval foramen, a small bone is attached, the other, the round foramen, has no attachment. These two openings are the approaches to the internal ear, and through them lies the course of the sonorous vibrations in their progress towards the auditory

nerve.

The small bones of the tympanum are named from their appearance as follows (beginning at the outermost): the malleus, or hammer, attached to the membrane of the tympanum; the incus, or anvil; and the stapes, or stirrup, which is fixed to the oval opening in the inner ear, called the fenestra ovalis. The incus is thus intermediate between the other two, and the result of the whole is, a species of angular and jointed connecting rod between the outer and inner walls of the tympanic cavity, which serves to communicate vibrations from the membrana tympani to the fluid contained in the vestibule of the internal ear.'

There are certain small muscles attached to those bones for the regulation of their movements. On the number of these muscles Anatomists are not agreed, owing to the minuteness and ambiguous appearance of the fibres. As to one of them there is no dispute, namely, the tensor tympani, a muscle inserted into the handle of the malleus, and by its contraction drawing inwards and tightening the membrane of the tympanum. A second muscle, admitted by most anatomists, is that named the stapedius, from its attachment to the stapes, or stirrup-bone, at the other end of the chain from the malleus. Mr. Toynbee considers the action of these two muscles as antagonistic.

The internal ear, or labyrinth, which is the essential or sensory part of the organ of hearing, is contained in the petrous portion of the temporal bone. It is made up of two very different structures, known respectively as the osseous and membranous labyrinth.'

(1.) The osseous labyrinth is lodged in the cancellated structure of the temporal bone, and presents, when separated

FIG. 7.*

from this, the appearance shown in the enlarged figure. It is incompletely divided into three parts, named respectively the vestibule, the semicircular canals, and the cochlea. They are lined throughout by a thin serous membrane, which secretes a clear fluid.

(2.) The membranous labyrinth is contained within the bony labyrinth, and, being smaller than it, a space intervenes between the two, which is occupied with the clear fluid just referred to. This structure supports the numerous minute ramifications of the auditory nerve, and encloses a liquid secretion.'

The minute anatomy of these parts I must pass over. The vestibule is the central chamber of the mass, and is the portion

An enlarged view of the labyrinth from the outer side:-1. Vestibule. 2. Fenestra ovalis. 3. Superior semicircular canal, 4. External semicircular canal. 5. Posterior semicircular canal. 6. First turn of the cochlea. 7. Second turn. 8. Apex of cochlea. 9. Fenestra rotunda. * Ampullæ of semicircular canal.-The smaller figure represents the osseous labyrinth of the natural size.'-(QUAIN.)