so widely spread, that in disease of the ear the resources of medicine are of little avail is justified, its grounds are chiefly two; first the ignorance which until lately invested the whole subject, and secondly, the fact that even the diseases which are remediable are, when they have advanced beyond a certain stage, apt to be tedious in their progress, and especially to be discouraging on account of their liability to temporary relapses. This liability is in great part to be accounted for by the connection between the tympanum and the throat, which is so especially subject to atmospheric influences. But even in cases that on this ground seem to baffle hope, if the affection do not involve the nerve-structure, perseverance will almost always effect a satisfactory result; and such a result is the more often attained because, on the one hand, the hearing may be very considerably below the average with no appreciable inconvenience, and on the other an even extreme amount of permanent damage to the membrane, and to some of the parts contained within the tympanum, may co-exist with a very slightly diminished function. The membrane may be not only almost wholly wanting, but may be so altered as to form irregular fleshy or fibroid masses presenting no visible resemblance to its original structure, both malleus and incus may apparently have been lost, and yet the patient scarcely desire to hear better. Thus, indeed, there arises one of the most interesting problems that the study of diseases of the ear presentsthe real relation of the membrana tympani to the function

of the organ, which is by no means so simple as would at first appear.

Among points of interest in respect to the structure of the ear may be mentioned its markedly spiral form. It is true that, on an observant scrutiny, clear traces of a spiral form are visible in almost every organ of the body,* but perhaps in none, except the heart, is this fundamental mode of structure so plainly marked as in the ear. It is visible not only in the cochlea, but throughout; the meatus winds with a slight spiral turn-backwards, upwards, forwards, and downwards; the tympanic bone in which the membrane is inserted is a distinct spiral ring, as can be well seen before osseous union occurs; a line traversing the ossicula takes a spiral course; and in the canals, perhaps, this relation is most intensely marked. For not only is each canal in itself a segment of a spiral curve, but the relations of the three canals to each other, lying at right angles as they do, reveal the very secret of the spiral form, which represents indeed simply a continuous motion passing successively into these three directions. In this respect the ear is eminently typical of the whole body, displaying visibly a plan or law of structure which is none the less paramount elsewhere because it is more concealed.

It can, perhaps, hardly be doubted that this markedly

*For the illustration of this fact I may refer to a paper on "Physical Morphology," in the "Brit. and For. Med. Chir. Rev.," 1858. The paper is reprinted in “Life in Nature.”

spiral structure is of a functional value: for all motions tend to propagate themselves (at least thro' media in any degree resisting) in a spiral direction. The spiral lines formed on glass rods thrown into sonorous vibrations are well known, and Sir John Herschel remarks* that the waves of sound may be traced in expanding spirals in the air. In the meatus, this form becomes of practical importance, in respect to the removal of foreign bodies, the introduction of the cotton wool or other form of artificial membrane, syringing, &c.-The meatus acts as a resonator to certain tones of the fourth octave (c””—c ́ ́ ́ ́), especially to g''''.†

In respect to the functions of the different parts of the ear the most minute investigations have as yet failed to gain any finally satisfactory results. By means of threads of glass, starch granules, or the plumules of a feather, attached to the ossicles, it has been demonstrated that vibrations impinging on the membrane are transmitted through the chain of bones, which moves as a whole, and imparts corresponding motions to the fluid of the labyrinth.

Dr. Buck gives the following as the results of his

* Treatise on Sound, reprinted from the "Encyclopædia Britannica." + Helmholz: Lehre von den Tonempfindungen," p. 175.

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By Politzer, Lucae, and others: see the various volumes of the "Archiv fur Ohrenheilkunde," 1864 and subsequently; and more recently by Dr. A. H.Buck (who used grains of starch); "Archives of Ophthalmology and Otology," 1870, No. 2. For the completest details on all these points see Helmholz, "On the Mechanism of the Ossicles of the Ear." (Sydenham Society.)

experiments:-On the dead subject, with a glass tube attached to an organ pipe inserted into the meatus, the malleus may be made to make an excursion inwards of 0.43 mm. without injury; but this exceeds, probably very greatly, its motion during life. The axis of rotation of the malleus lies nearly midway between its two extremities, so that the head moves outwards as the end of the handle moves inwards. The rotation takes place upon a ligamentous structure passing from the malleus to the anterior and posterior walls of the membrane, and which is termed by Helmholz the axis-ligament. The upper part of the head of the malleus moves horizontally outwards, while the part below the articulation with the incus moves upwards as much as outwards; and the incus is so articulated with the malleus as to share this motion; so that it is carried upwards and outwards when the membrane is carried inwards by a wave of sound. But in addition to this motion the body of the incus is thrown slightly backwards, and the end of its long process slightly forwards. The stapes moves correspondingly; namely upwards, slightly inwards, and forwards. As a result of this, the upper and anterior border of the base of the stapes is driven farther into the vestibule than the lower and posterior border. Hence a displacement of the entire mass of the labyrinth-fluid ensues. An impulse given to the centre of the membrane is communicated from ossicle to ossicle, with a loss in the following ratio :

1

*

But this refers to the utmost excursions; when they are feeble, scarcely any loss occurs in the transmission, so that probably during life the proportion between the motions of the various bones is much more equal than that given above. Section of the tendons of the tensor tympani and stapedius had no effect on the motions. Helmholz found that the greatest natural motion of the stapes was 3 mm. If the ossicula lie firmly together, each excursion of the long process of the incus will equal only of that of the malleus handle; but the force it transmits to the stapes will be one and a half times as great as that which acts on the extremity of the malleus.

By an arrangement of the heads of the malleus and incus, after the fashion of a cog, both malleus and incus move together on pressure inwards; but the malleus may move very considerably outwards without carrying the incus with it, thus guarding in part against the effects of too powerful inflation of the drum.

According to Rüdinger, the malleus and incus and the incus and stapes are articulated by means of a true joint, containing a freely movable meniscus of cartilage, like that of the clavicle. The articulation of the stapes with the fenestra ovalis belongs to the group of the

* "Mechanism of the Ossicles of the Ear."