genital formations of this kind were originally intended for school. masters and schoolma'ams, but the fall of man has so mixed up things, that cross-eyes seem to present themselves here and there without a particle of reference to avocation, and school-boys are not often enough afflicted with teachers having them.

In the annexed illustration, a represents a single convergent squint; b, a double convergent squint; c, a double divergent squint; and d a convergent and divergent squint. The displacement of the eye in any one of the cases illustrated, if congenital, or in other words, when the person affected was born so, results from the natural contraction of one set of muscles, and the natural extension or relaxation of those on the opposite side; but this same position of the eyes may be produced by disease affecting the muscles; or it may be acquired by practising it for sport; or a weakness of one set of muscles and a contraction of the other may gradually take place without any visible Strabismus generally must be treated both medically and surgically, and in my surgical department all operations of this kind are performed in a few seconds, by an experienced operator, who does the work so expertly as to give the patient scarcely a particle of pain. When there is cerebral affection or weakness of the eyes, medication alone will sometimes overcome the difficulty, but if not, it should either precede or immediately follow an operation.

cause.

Other Diseases of the Eye

Fig. 113.

A

В

Will not be presented here, as more space than was originally apportioned to this division of the chapter is already occupied. 1

will, therefore, call the reader's attention to diseases of the ear, after remarking that all affected with any diseases of the eyes, are at liberty to consult the author in relation thereto. In all letters of con sultation, answers to the questions on page 583 should be given.

Defective Hearing.

If the non-professional reader could follow me through all the circuitous paths of the ear without becoming befogged with the technical names anatomists have bestowed upon the various organs therein; if the common mind could be made conversant with the complex physical machinery of the organs of hearing; and then, if we could all of us comprehend the mysterious, ever-hidden connection existing between the physical organs of sense and the conscious principle, we might cease to wonder at, but never to admire, the peculiar mechanism by which all of us, gifted with the sense of hearing, are made conscious of so much that is passing in the material world through that remarkable something we familiarly denominate sound.

Your friend speaks to you. How are you made aware of the fact, and of the impression he wishes to convey to your mind? He expels from his lungs currents of air, shaped by the organs of the throat and modified and chopped off here and there by the motions of the tongue and lips, so that the air moves toward you in what may be called articulate waves. These fall upon the external ear, a perfect acoustic instrument, which is so modeled as to conduct them into the orifice, where they soon come in contact with the ear-drum, technically called the tympanum. This instantly vibrates in perfect accord with the motions of the articulate waves, and the vibrations of this organ in turn set in motion other waves in the air confined in the cavity beyond, when motion is communicated to reeds of delicate bones the smallest bones in the body-and to fibres of muscle, which vibrate like the reeds of an organ when acted upon by cur rents of air, or the strings of a violin when agitated by the finger or bow. Thus further modified and intensified, these waves move onward through irregular cavities, circuitous canals, convoluted tubes, and delicate membranes, all of the most wonderful complexity, until reaching the labyrinth, or parlor of the ear, where there are cushions of fluids upon which they fall and set in motion multitudinous little granules of calcareous matter, whose seitation frictionizes

the sensitive, minute branches of the auditory nerve, which penetrate the sacs confining the granules. This influence conveys to the mind what is commonly called sound; but just how this is affected no human anatomist or physiologist is likely ever to be able to determine.

Considering the complexity of all this hearing machinery, and the delicacy of the various parts composing it, exceeding in some respects the wonderful mechanism of the eye, it is not at all strange that many are affected with partial and some with entire deafness.

Not a single tube can be closed, not a bone or fibre destroyed, not a particle of change in quantity or quality of the fluids of the sacs, or those moistening or bathing the membrane lining the canals or cavities, occur, without affecting the accuracy of the impressions conveyed to the mind through the mechanism of the ear.

Let us briefly look into the most common causes of defective hearing. We will commence as soon as we penetrate the orifice. In what is called the external opening, between the outer orifice and

the ear-drum, there are yellowish colored glands which pour out upon the lining of this canal a fatty, albuminous, yellow substance, possessing some of the properties of bile, which we call the ear-wax. The true office of this secretion, is probably to exclude insects from the ear, as it is disagreeably bitter and adhesive. Flies, mosquitoes fleas, and the minute inhabitants of the tenement bed-chamb could make as little headway through this secretion as they could through molasses, while its flavor to their epicurean teeth would be far less palatable. So long as this secretion is not deficient, excessive, or vitiated, this portion of the ear generally performs its func tion properly. But if it dries up, insects may nestle there, irritate the canal, and obstruct the vibrations of the air; if it becomes excessive, or gluey and dense, then the canal is obstructed, and in some cases completely filled up. A deficiency, excess, or vitiation of this secretion, called ear-wax, may therefore render the hearing defective.

The external opening of the ear terminates with an organ called the tympanum or car-drum, a membrane nearly circular in form, and fastened in a bony ring. Its external surface forms a conical concavity, highly polished, and in the living subject the membrane is nearly transparent. Naturally it is without orifice, but in some persons, by disease or accident, it may have become slightly perforated without materially affecting the hearing. If, however, this organ be greatly perforated, or nearly or quite obliterated; or if it be thickened or indurated; or if the muscles controlling it be weakened or destroyed, hearing may be defective or lost altogether.

The inner side of the ear-drum is what is called the cavity of the tympanum. This must be supplied with air to make the hearing complete. The air reaches it by what is called the Eustachian tube, which opens like a trumpet, large enough to insert the little finger, in the throat, and extends along upward and backward, for nearly two inches, when it opens into this cavity; but the lining of the Jatter secretes a mucus, with which to moisten its walls, and in disease this secretion may be thick and excessive, in which case it fills up the Eustachian tube, and thereby excludes air from this cavity, and in many cases fills the cavity itself. Or, if the mastoid cells or sinuses, which have an opening in the cavity of the tympanum, nearly opposite the Eustachian tube, be the seat of irritation, the secretions of these may deluge the cavity or clog the tube. In some cases, these walls, cavities, and tubes are affected with catarrh, and

become congested with catarrhal matter. Whenever or however they are obstructed, the person so affected cannot hear distinctly, if at all.

It sometimes happens that the labyrinth, with all its delicate appurtenances, becomes the seat of disease, obstructing communication with the tympanum, or causing such a change in the fluids of the sacs containing the calcareous granules, that the auditory nerve fails to receive any impression from the vibrations going on in the tympanum, or its vicinity. In either case, partial or entire deafness

must ensue.

Ulcerations sometimes take place in the delicate organs of the ear. It is terrible to have such visitations here, for they are liable to destroy the walls of the tubes, canals, and cavities; to eat away entirely the ear-drum, and to break up and destroy the delicate bones and muscles, forming the reeds and strings, and to expel them through the external opening in the form of offensive matter. Entire deafness sometimes results from these ulcerations.

No form of disease, however, can be more complete than that caused by paralysis of the auditory nerve. All the other organs of the ear may be in complete order, and mechanically vibrate to every atmospheric impulse. The articulate waves may move along regularly through all the natural cavities and tubes, and enter the labyrinth with the greatest precision and order; they may set in motion all those peculiar little granules which play upon the termini of the auditory nerve, but if the latter be paralyzed, no intelligence whatever is conveyed to the brain. This line of telegraph is practically down, and although the brain may be in communication with the external world by telegraphic connection with the eyes and other organs of sense, no message whatever is received via eardom. The approach of paralysis of the auditory nerve is usually heralded by noises in the head, ringing and roaring in the ears, and, in some cases, by acute pain. There are constantly motions taking place in the atmosphere of so slight a nature that the healthy auditory nerve is not impressed by them. If you please to call them sounds, then there are sounds of which the normal auditory nerve takes no notice. But when that nerve becomes irritated or inflamed-as sensitive as a tender tooth-it feels every impulse of the air, however slight, and considering the forms of the canals through which these impulses pass, the sensation conveyed through the irritated