This consists, first, of a gland for the secretion of the tears, and, second, of a series of ca.n.a.ls for the conveyance of the superfluous tears into the cavity of the nose.
The gland is situated above the outer part of the eyeball, and the tears which have flowed over the eye and reached the inner angle are there directed by a small, conical papilla (lacrimal caruncle) into two minute orifices, and thence by two ducts (lacrimal) to a small pouch (lacrimal sac) from which a ca.n.a.l leads through the bones of the face into the nose. This opens in the lower part of the nose on the floor of the pa.s.sage and a little outside the line of union of the skin which lines the false nostril with the mucous membrane of the nose. In the a.s.s and mule this opening is situated on the roof instead of the floor of the nose, but still close to the external opening.
EXAMINATION OF THE EYE.
To avoid unnecessary repet.i.tion the following general directions are given for the examination of the eye: The eye, and to a certain extent the mucous membrane lining the eyelids, may be exposed to view by gently parting the eyelids with the thumb and forefinger pressed on the middle of the respective lids. The pressure, it is true, causes the protrusion of the haw over a portion of the lower and inner part of the eye, but by gentleness and careful graduation of the pressure this may be kept within bounds, and oftentimes even the interior of the eye can be seen.
As a rule it is best to use the right hand for the left eye, and the left hand for the right, the finger in each case being pressed on the upper lid while the thumb depresses the lower one. In cases in which it is desirable to examine the inner side of the eyelid further than is possible by the above means, the upper lid may be drawn down by the eyelashes with the one hand and then everted over the tip of the forefinger of the other hand, or over a probe laid flat against the middle of the lid. When the interior of the eye must be examined it is useless to make the attempt in the open sunshine or under a clear sky.
The worst cases, it is true, can be seen under such circ.u.mstances, but for the slighter forms the horse should be taken indoors, where all light from above will be shut off, and should be placed so that the light may fall on the eye from the front and side. Then the observer, placing himself in front of the animal, will receive the reflected rays from the cornea, the front of the lens and the back, and can much more easily detect any cloudiness, opacity, or lack of transparency. The examination can be made much more satisfactory by placing the horse in a dark chamber and illuminating the eye by a lamp placed forward and outward from the eye which is to be examined. Any cloudiness is thus easily detected, and any doubt may be resolved by moving the lamp so that the image of the flame may be pa.s.sed in succession over the whole surface of the transparent cornea and of the crystalline lens. Three images of the flame will be seen, the larger one upright, reflected from the anterior surface of the eye; a smaller one upright, reflected from the anterior surface of the lens; and a second small one inverted from the back surface of the lens.
So long as these images are reflected from healthy surfaces they will be clear and perfect in outline, but as soon as one strikes on an area of opacity it will become diffused, cloudy, and indefinite. Thus, if the large, upright image becomes hazy and imperfect over a particular spot of the cornea, that will be found to be the seat of disease and opacity.
Should the large image remain clear, but the small upright one become diffuse and indefinite over a given point, it indicates opacity on the front of the capsule of the lens. If both upright images remain clear while the inverted one becomes indistinct at a given point, then the opacity is in the substance of the lens itself or in the posterior part of its capsule.
If in a given case the pupil remains so closely contracted that the deeper parts of the eye can not be seen, the eyelids may be rubbed with extract of belladonna, and in a short time the pupil will be found widely dilated.
DISEASES OF THE EYELIDS.
CONGENITAL DISORDERS.
Some faulty conditions of the eyelids are congenital, as division of an eyelid in two, after the manner of harelip, abnormally small opening between the lids, often connected with imperfect development of the eye, and closure of the lids by adhesion. The first is to be remedied by paring the edges of the division and then bringing them together, as in torn lids. The last two, if remediable at all, require separation by the knife, and subsequent treatment with a cooling astringent eyewash.
NERVOUS DISORDERS.
SPASM OF EYELIDS may be owing to const.i.tutional susceptibility, or to the presence of local irritants (insects, chemical irritants, sand, etc.) in the eye, to wounds or inflammation of the mucous membrane, or to disease of the brain. When due to local irritation it may be temporarily overcome by instilling a few drops of a 4 per cent solution of cocaine into the eye, when the true cause may be ascertained and removed. The nervous or const.i.tutional disease must be treated according to its nature.
DROOPING EYELIDS, OR PTOSIS.--This is usually present in the upper lid, or is at least little noticed in the lower. It is sometimes but a symptom of paralysis of one-half of the face, in which case the ear, lips, and nostrils on the same side will be found soft, drooping, and inactive, and even the half of the tongue may partake of the palsy. If the same condition exists on both sides, there is difficult, snuffling breathing, from the air drawing in the flaps of the nostrils in inspiration, and all feed is taken in by the teeth, as the lips are useless. In both there is a free discharge of saliva from the mouth during mastication. This paralysis is a frequent result of injury, by a poke, to the seventh nerve, as it pa.s.ses over the back of the lower jaw.
In some cases the paralysis is confined to the lid, the injury having been sustained by the muscles which raise it, or by the supraorbital nerve, which emerges from the bone just above the eye. Such injury to the nerve may have resulted from fracture of the orbital process of the frontal bone above the eyeball.
The condition may, however, be due to spasm of the sphincter muscle, which closes the lids, or to inflammation of the upper lid, usually a result of blows on the orbit. In the latter case it may run a slow course with chronic thickening of the lid.
The paralysis due to the poke may be often remedied, first, by the removal of any remaining inflammation by a wet sponge worn beneath the ear and kept in place by a bandage; secondly, when all inflammation has pa.s.sed, by a blister on the same region, or by rubbing it daily with a mixture of olive oil and strong aqua ammonia in equal proportions.
Improvement is usually slow, and it may be months before complete recovery ensues.
In paralysis from blows above the eyes the same treatment may be applied to that part.
Thickening of the lid may be treated by painting with tincture of iodin, and that failing, by cutting out an elliptical strip of the skin from the middle of the upper lid and st.i.tching the edges together.
INFLAMMATION OF THE EYELIDS.
The eyelids suffer more or less in all severe inflammations of the eye, whether external or internal, but inasmuch as the disease sometimes starts in the lids and at other times is exclusively confined to them, it deserves independent mention.
Among the causes may be named: Exposure to drafts of cold air, or to cold rain or snow storms; the bites or stings of mosquitoes, flies, or other insects; snake bites, p.r.i.c.ks with thorns, blows of whip or club; accidental bruises against the stall or ground, especially during the violent struggles of colic, enteritis, phrenitis (staggers), and when thrown for operations. It is also a result of infecting inoculations, as of erysipelas, anthrax, boil, etc., and is noted by Leblanc as especially prevalent among horses kept on low, marshy pastures. Finally, the introduction of sand, dust, chaff, beards of barley and seeds of the finest gra.s.ses, and the contact with irritant, chemical powders, liquids, and gases (ammonia from manure or factory, chlorin, strong sulphur fumes, smoke, and other products of combustion, etc.) may start the inflammation. The eyelids often undergo extreme inflammatory and dropsical swelling in urticaria (nettlerash, surfeit) and in the general inflammatory dropsy known as purpura hemorrhagica.
The affection will, therefore, readily divide itself into (1) inflammations due to const.i.tutional causes; (2) those due to direct injury, mechanical or chemical; and (3) such as are due to inoculation with infecting material.
(1) Inflammations due to const.i.tutional causes are distinguished by the absence of any local wound, and the history of a low, damp pasture, exposure, indigestion from unwholesome feed, or the presence elsewhere on the limbs or body of the general, doughy swellings of purpura hemorrhagica. The lids are swollen and thickened; it may be slightly or it may be so extremely that the eyeball can not be seen. If the lid can be everted to show its mucous membrane, that is seen to be of a deep-red color, especially along the branching lines of the blood vessels. The part is hot and painful, and a profuse flow of tears and mucus escapes on the side of the face, causing irritation and loss of the hair. If improvement follows, this discharge becomes more tenacious, and tends to cause adhesion to the edges of the upper and lower lids and to mat together the eyelashes in bundles. This gradually decreases to the natural amount, and the redness and congested appearance of the eye disappears, but swelling, thickening, and stiffness of the lids may continue for a time. There may be more or less fever according to the violence of the inflammation, but so long as there is no serious disease of the interior of the eye or of other vital organ, it is usually moderate.
The local treatment consists in astringent, soothing lotions (sugar of lead 30 grains, laudanum 2 teaspoonfuls, rain water--boiled and cooled--1 pint), applied with a soft cloth kept wet with the lotion, and hung over the eye by tying it to the headstall of the bridle on the two sides. If the mucous membrane lining of the lids is the seat of little red granular elevations, a drop of solution of 2 grains of nitrate of silver in an ounce of distilled water should be applied with the soft end of a clean feather to the inside of the lid twice a day. The patient should be removed from all such conditions (pasture, faulty feed, exposure, etc.) as may have caused or aggravated the disease, and from dust and irritant fumes and gases. He should be fed from a manger high enough to favor the return of blood from the head, and should be kept from work, especially in a tight collar which would prevent the descent of blood by the jugular veins. The diet should be laxative and nonstimulating (gra.s.s, bran mashes, carrots, turnips, beets, potatoes, or steamed hay), and any costiveness should be corrected by a mild dose of raw linseed oil (1 to 1-1/2 pints). In cold weather warm blanketing may be needful, and even loose flannel bandages to the limbs, but heat should never be sought at the expense of pure air.
(2) In inflammations due to local irritants of a noninfective kind a careful examination will usually reveal their presence, and the first step must be their removal with a pair of blunt forceps or the point of a lead pencil. Subsequent treatment will be in the main the local treatment advised above.
(3) In case of infective inflammation there will often be found a p.r.i.c.k or tear by which the septic matter has entered, and in such case the inflammation will for a time be concentrated at that point. A round or conical swelling around an insect bite is especially characteristic. A snake bite is marked by the double p.r.i.c.k made by the two teeth and by the violent and rapidly spreading inflammation. Erysipelas is attended with much swelling, extending beyond the lids and causing the mucous membrane to protrude beyond the edge of the eyelid (chemosis). This is characterized by a bright, uniform, rosy red, disappearing on pressure, or later by a dark, livid hue, but with less branching redness than in noninfecting inflammation and less of the dark, dusky, brownish or yellowish tint of anthrax. Little vesicles may appear on the skin, and pus may be found without any distinct limiting membrane, as in abscess.
It is early attended with high fever and marked general weakness and inappetence. Anthrax of the lids is marked by a firm swelling, surmounted by a blister, with b.l.o.o.d.y serous contents, which tends to burst and dry up into a slough, while the surrounding parts become involved in the same way. Or it may show as a diffuse, dropsical swelling, with less of the hard, central sloughing nodule, but, like that, tending to spread quickly. In both cases alike the mucous membrane and the skin, if white, a.s.sumes a dusky-brown or yellowish-brown hue, which is largely characteristic. This may pa.s.s into a black color by reason of extravasation of blood. Great const.i.tutional disturbance appears early, with much prostration and weakness and generalized anthrax symptoms.
_Treatment._--The treatment will vary according to the severity. Insect bites may be touched with a solution of equal parts of glycerin and aqua ammonia, or a 10 per cent solution of carbolic acid in water. Snake bites may be bathed with aqua ammonia, and the same agent given in doses of 2 teaspoonfuls in a quart of water, or alcohol may be given in pint or quart doses, according to the size of the animal. In erysipelas the skin may be painted with tincture of chlorid of iron, or with a solution of 20 grains of iodin in an ounce of carbolic acid, and one-half an ounce of tincture of chlorid of iron may be given thrice daily in a bottle of water. In anthrax the swelling should be painted with tincture of iodin, or of the mixture of iodin and carbolic acid, and if very threatening it may have the tincture of iodin injected into the swelling with a hypodermic syringe, or the hard ma.s.s may be freely incised to its depth with a sharp lancet and the lotion applied to the exposed tissues.
Internally, iodid of pota.s.sium may be given in doses of 2 drams thrice a day, or tincture of the chlorid of iron every four hours.
STY, OR FURUNCLE (BOIL) OF THE EYELID.
This is an inflammation of limited extent, advancing to the formation of matter and the sloughing out of a small ma.s.s of the natural tissue of the eyelid. It forms a firm, rounded swelling, usually near the margin of the lid, which suppurates and bursts in four or five days. Its course may be hastened by a poultice of camomile flowers, to which have been added a few drops of carbolic acid, the whole applied in a very thin muslin bag. If the swelling is slow to open after having become yellowish white, it may be opened by a lancet, the incision being made at right angles to the margin of the lid.
ENTROPION AND ECTROPION, OR INVERSION AND EVERSION OF THE EYELID.
These are respectively caused by wounds, sloughs, ulcers, or other causes of loss of substance of the mucous membrane on the inside of the lid and of the skin on the outside; also of tumors, skin diseases, or paralysis which leads to displacement of the margin of the eyelid. As a rule, they require a surgical operation, with removal of an elliptical portion of the mucous membrane or skin, as the case may be, but which requires the skilled and delicate hand of the surgeon.
TRICHIASIS.
This consists in the turning in of the eyelashes so as to irritate the front of the eye. If a single eyelash, it may be snipped off with scissors close to the margin of the eyelid or pulled out by the root with a pair of flat-bladed forceps. If the divergent lashes are more numerous, the treatment may be as for entropion, by excising an elliptical portion of skin opposite the offending lashes and st.i.tching the edges together, so as to draw outward the margin of the lid at that point.
WARTS AND OTHER TUMORS OF THE EYELIDS.
The eyelids form a favorite site for tumors, and above all, warts, which consist in a simple diseased overgrowth (hypertrophy) of the surface layers of the skin. If small, they may be snipped off with scissors or tied around the neck with a stout, waxed thread and left to drop off, the destruction being completed, if necessary, by the daily application of a piece of sulphate of copper (blue vitriol), until any unhealthy material has been removed. If more widely spread, the wart may still be clipped off with curved scissors or knife, and the caustic thoroughly applied day by day.
A bleeding wart, or erectile tumor, is more liable to bleed, and is best removed by constricting its neck with the waxed cord or rubber band, or if too broad it may be transfixed through its base by a needle armed with a double thread, which is then to be cut in two and tied around the two portions of the neck of the tumor. If still broader, the armed needle may be carried through the base of the tumor at regular intervals, so that the whole may be tied in moderately sized sections.
In gray and in white horses black, pigmentary tumors (melanotic) are common on the black portions of skin, such as the eyelids, and are to be removed by scissors or knife, according to their size. In the horse they do not usually tend to recur when thoroughly removed, but at times they prove cancerous (as is the rule in man), and then they tend to reappear in the same site or in internal organs with, it may be, fatal effect.
Encysted, honeylike (melicerous), sebaceous, and fibrous tumors of the lids all require removal with the knife.
TORN EYELIDS OR WOUNDS OF EYELIDS.
The eyelids are torn by attacks with horns of cattle, or with the teeth, or by getting caught on nails in stall, rack, or manger, on the point of stumps, fences, or fence rails, on the barbs of wire fences, and on other pointed bodies. The edges should be brought together as promptly as possible, so as to effect union without the formation of matter, puckering of the skin, and unsightly distortions. Great care is necessary to bring the two edges together evenly without twisting or puckering. The simplest mode of holding them together is by a series of sharp pins pa.s.sed through the lips of the wound at intervals of not more than a third of an inch, and held together by a thread twisted around each pin in the form of the figure 8, and carried obliquely from pin to pin in two directions, so as to prevent gaping of the wound in the intervals. The points of the pins may then be cut off with scissors, and the wound may be wet twice a day with a weak solution of carbolic acid.
TUMOR OF THE HAW, OR CARIES OF THE CARTILAGE.
Though cruelly excised for alleged "hooks," when itself perfectly healthy, in the various diseases which lead to retraction of the eye into its socket, the haw may, like other bodily structures, be itself the seat of actual disease. The pigmentary, black tumors of white horses and soft (encephaloid) cancer may attack this part primarily or extend to it from the eyeball or eyelids; hairs have been found growing from its surface, and the mucous membrane covering it becomes inflamed in common with that covering the front of the eye. These inflammations are but a phase of the inflammation of the external structures of the eye, and demand no particular notice nor special treatment. The tumors lead to such irregular enlargement and distortion of the haw that the condition is not to be confounded with the simple projection of the healthy structure over the eye when the lids are pushed apart with the finger and thumb, and the same remark applies to the ulceration, or caries, of the cartilage. In the latter case, besides the swelling and distortion of the haw, there is this peculiarity, that in the midst of the red inflamed ma.s.s there appears a white line or ma.s.s formed by the exposed edge of the ulcerating cartilage. The animal having been thrown and properly fixed, an a.s.sistant holds the eyelids apart while the operator seizes the haw with forceps or hook and carefully dissects it out with blunt-pointed scissors. The eye is then covered with a cloth, kept wet with an eyewash, as for external ophthalmia.