As already stated, the pharynx is common to the functions of both respiration and alimentation. From this organ the air pa.s.ses into the larynx and thence onward to the lungs. In the posterior part of the pharynx is the superior extremity of the gullet, the ca.n.a.l through which the feed and water pa.s.s to the stomach. Inflammation of the pharynx is a complication of other diseases--namely, influenza, strangles, etc.--and is probably always more or less complicated with inflammation of the larynx. That it may exist as an independent affection there is no reason to doubt, and it is discussed as such with the diseases of the digestive tract.

SORE THROAT, OR LARYNGITIS.

The larynx is situated in the s.p.a.ce between the lower jawbones just back of the root of the tongue. It may be considered as a box (somewhat depressed on each side), composed princ.i.p.ally of cartilages and small muscles, and lined on the inside with a continuation of the respiratory mucous membrane. Posteriorly it opens into and is continuous with the windpipe. It is the organ of the voice, the vocal cords being situated within it; but in the horse this function is of little consequence. It dilates and contracts to a certain extent, thus regulating the volume of air pa.s.sing through it. The mucous membrane lining it internally is so highly sensitive that if the smallest particle of feed happens to drop into it from the pharynx violent coughing ensues instantly and is continued until the source of irritation is ejected. This is a provision of nature to prevent foreign substances gaining access to the lungs.

That projection called Adam's apple in the neck of man is the prominent part of one of the cartilages forming the larynx.

Inflammation of the larynx is a serious and sometimes fatal disease, and, as before stated, is usually complicated with inflammation of the pharynx, const.i.tuting what is popularly known as "sore throat." The chief causes are chilling and exposure.

_Symptoms._--About the first symptom noticed is cough, followed by difficulty in swallowing, which may be due to soreness of the membrane of the pharynx, over which the feed or water must pa.s.s, or from the pain caused by the contraction of the muscles necessary to impel the feed or water onward to the gullet; or this same contraction of the muscles may cause a pressure on the larynx and produce pain. In many instances the difficulty in swallowing is so great that water, and in some cases feed, is returned through the nose. This, however, does not occur in laryngitis alone, but only when the pharynx is involved in the inflammation. The glands between the lower jawbones and below the ears may be swollen. Pressure on the larynx induces coughing. The head is more or less "poked out," and has the appearance of being stiffly carried. The membrane in the nose becomes red. A discharge from the nostrils soon appears. As the disease advances, the breathing may a.s.sume a more or less noisy character; sometimes a harsh, rasping snore is emitted with every respiration, the breathing becomes hurried, and occasionally the animal seems threatened with suffocation.

_Treatment._--In all cases steam the nostrils, as has been advised for cold in the head. In bad cases cause the steam to be inhaled continuously for hours--until relief is afforded. Have a bucketful of fresh boiling water every fifteen or twenty minutes. In each bucketful of water put a tablespoonful of oil of turpentine, or compound tincture of benzoin, the vapor of which will be carried along with the steam to the affected parts and have a beneficial effect. In mild cases steaming the nostrils five, six, or seven times a day will suffice.

The animal should be placed in a comfortable, dry stall (a box stall preferred), and should have pure air to breathe. The body should be blanketed, and bandages applied to the legs. The diet should consist of soft feed--bran mashes, scalded oats, linseed gruel, and, best of all, fresh gra.s.s, if in season. The manger, or trough, should neither be too high nor too low, but a temporary one should be constructed at about the height he carries his head. Having to reach too high or too low may cause so much pain that the animal would rather forego satisfying what little appet.i.te he may have than inflict pain by craning his head for feed or water. A supply of fresh water should be before him all the time; he will not drink too much, nor will the cold water hurt him.

Constipation (if present) must be relieved by enemas of warm water, administered three or four times during the twenty-four hours.

A liniment composed of 2 ounces of olive oil and 1 each of solution of ammonia and tincture of cantharides, well shaken together, may be thoroughly rubbed in about the throat from ear to ear, and about 6 inches down over the windpipe, and in the s.p.a.ce between the lower jaws.

This liniment should be applied once a day for two or three days.

If the animal is breathing with great difficulty, persevere in steaming the nostrils, and dissolve 2 drams of chlorate of pota.s.sium in every gallon of water he will drink; even if he can not swallow much of it, and even if it is returned through the nostrils, it will be of some benefit to the pharynx as a gargle.

An electuary of acetate of potash, 2 drams, honey, and licorice powder may be spread on the teeth with a paddle every few hours. If the pain of coughing is great, 2 or 3 grains of morphin may be added to the electuary.

When the breathing begins to be loud, relief is afforded in some cases by giving a drench composed of 2 drams of fluid extract of jaborandi in half a pint of water. If benefit is derived, this drench may be repeated four or five hours after the first dose is given. It will cause a free flow of saliva from the mouth.

In urgent cases, when suffocation seems inevitable, the operation of tracheotomy must be performed. To describe this operation in words that would make it comprehensible to the general reader is a more difficult task than performing the operation, which, in the hands of the expert, is simple and attended with little danger.

The operator should be provided with a tracheotomy tube (to be purchased from any veterinary instrument maker) and a sharp knife, a sponge, and a bucket of clean cold water. The place to be selected for opening the windpipe is that part which is found, upon examination, to be least covered with muscles, about 5 or 6 inches below the throat. Right here, then, is the place to cut through. Have an a.s.sistant hold the animal's head still. Grasp your knife firmly in the right hand, select the spot and make the cut from above to below directly on the median line on the anterior surface of the windpipe. Make the cut about 2 inches long in the windpipe; this necessitates cutting three or four rings. One bold stroke is usually sufficient, but if it is necessary to make several other cuts to finish the operation, do not hesitate. Your purpose is to make a hole in the windpipe sufficiently large to admit the tracheotomy tube. It is quickly manifested when the windpipe is severed; the hot air rushes out, and when air is taken in it is sucked in with a noise. A slight hemorrhage may result (it never amounts to much), which is easily controlled by washing the wound with a sponge and cold water, but use care not to get any water in the windpipe. Do not neglect to instruct your a.s.sistant to hold the head down immediately after the operation, so that the neck will be in a horizontal line. This will prevent the blood from getting into the windpipe and will allow it to drop directly on the ground. If you have the self-adjustable tube, it retains its place in the wound without further trouble after it is inserted. The other kind requires to be secured in position by means of two tapes or strings tied around the neck. After the hemorrhage is somewhat abated, sponge the blood away and see that the tube is thoroughly clean, then insert it, directing the tube downward toward the lungs.

The immediate relief this operation affords is gratifying to behold. The animal, a few minutes before on the verge of death from suffocation, emitting a loud wheezing sound with every breath, with haggard countenance, body swaying, pawing, gasping, fighting for breath, now breathes tranquilly, and may be in search of something to eat.

The tube should be removed once a day and cleaned with carbolic-acid solution (1 to 20), and the discharge washed away from the wound with a solution of carbolic acid, 1 part to 40 parts water. Several times a day the hand should be held over the opening in the tube to test the animal's ability to breathe through the nostrils, and as soon as it is demonstrated that breathing can be performed in the natural way the tube should be removed, the wound thoroughly cleansed with carbolic-acid solution (1 to 40), and closed by inserting four or five st.i.tches through the skin and muscle. Do not include the cartilages of the windpipe in the st.i.tches. Apply the solution to the wound three or four times a day until healed. When the tube is removed to clean it the lips of the wound may be pressed together to ascertain whether or not the horse can breathe through the larynx. The use of the tube should be discontinued as soon as possible.

It is true that tracheotomy tubes are seldom to be found on farms, and especially when most urgently required. In such instances there is nothing left to be done but, with a strong needle, pa.s.s a waxed end or other strong string through each side of the wound, including the cartilage of the windpipe, and keep the wound open by tying the strings over the neck.

During the time the tube is used the other treatment advised must not be neglected. After a few days the discharge from the nostrils becomes thicker and more profuse. This is a good symptom and signifies that the acute stage has pa.s.sed. At any time during the attack, if the horse becomes weak, give whisky or aromatic spirits of ammonia, 2 ounces in water. Do not be in a hurry to put the animal back to work, but give plenty of time for a complete recovery. Gentle and gradually increasing exercise may be given as soon as the horse is able to stand it. The feed should be carefully selected and of good quality. Tonics, as iron or a.r.s.enic, may be employed.

If abscesses form in connection with the disease they must be opened to allow the escape of pus, but do not rashly plunge a knife into swollen glands; wait until you are certain the swelling contains pus. The formation of pus may be encouraged by the constant application of poultices for hours at a time. The best poultice for the purpose is made of linseed meal, with sufficient hot water to make a thick paste. If the glands remain swollen for some time after the attack, rub well over them an application of the following: Biniodid of mercury, 1 dram; lard, 1 ounce; mix well. This may be applied once every day until the part is blistered.

Sore throat is also a symptom of other diseases, such as influenza, strangles, purpura hemorrhagica, etc., which diseases may be consulted under their proper headings.

After a severe attack of inflammation of the larynx the mucous membrane may be left in a thickened condition, or an ulceration of the part may ensue, either of which is liable to produce a chronic cough. For the ulceration it is useless to prescribe, because it can neither be diagnosed nor topically treated by the nonprofessional.

If a chronic cough remains after all the other symptoms have disappeared, it is advisable to give 1 dram of iodid of pota.s.sium dissolved in a bucketful of drinking water, one hour before feeding, three times a day for a month if necessary. Also rub in well the preparation of iodid of mercury (as advised for the swollen glands) about the throat, from ear to ear, and in the s.p.a.ce between the lower jawbones. The application may be repeated every third day until the part is blistered.

SPASM OF THE LARYNX.

The symptoms are as follows: Sudden seizure by a violent fit of coughing; the horse may reel and fall, and after a few minutes recover and be as well as ever. The treatment recommended is this: Three drams of bromid of pota.s.sium three times a day, dissolved in the drinking water, or give as a drench in about a half pint of water for a week.

Then give 1 dram of powdered nux vomica (either on the food or shaken with water as a drench) once a day for a few weeks.

CROUP AND DIPHTHERIA.

Neither of these diseases affects the horse, but these names are sometimes wrongly applied to severe laryngitis or pharyngitis, or to forage poisoning, in which the throat is paralyzed and becomes excessively inflamed and gangrenous.

THICK WIND AND ROARING.

Horses that are affected with chronic disease that causes a loud, unnatural noise in breathing are said to have thick wind, or to be roarers. This cla.s.s does not include those affected with severe sore throat, as in these cases the breathing is noisy only during the attack of the acute disease.

Thick wind is caused by an obstruction to the free pa.s.sage of the air in some part of the respiratory tract. Nasal polypi, thickening of the membrane, pharyngeal polypi, deformed bones, paralysis of the wing of the nostril, etc., are occasional causes. The noisy breathing of horses after having been idle and put to sudden exertion is not due to any disease and is only temporary. Very often a nervous, excitable horse will make a noise for a short time when started off, generally caused by the cramped position in which the head and neck are forced in order to hold him back.

Many other causes may occasion temporary, intermittent, or permanent noisy respiration, but chronic roaring is caused by paralysis of the muscles of the larynx; and almost invariably it is the muscles of the left side of the larynx that are affected.

In chronic roaring the noise is made when the air is drawn into the lungs; only when the disease is far advanced is a sound produced when the air is expelled, and even then it is not nearly so loud as during inspiration.

In a normal condition the muscles dilate the aperture of the larynx by moving the cartilage and vocal cord outward, allowing a sufficient volume of air to rush through. But when the muscles are paralyzed the cartilage and vocal cord that are normally controlled by the affected muscles lean into the tube of the larynx, so that when the air rushes in it meets this obstruction and the noise is produced. When the air is expelled from the lungs its very force pushes the cartilage and vocal cords out, and consequently noise is not produced in the expiratory act.

The paralysis of the muscles is due to derangement of the nerve that supplies them with energy. The muscles of both sides are not supplied by the same nerve; there is a right and a left nerve, each supplying its respective side. The reason why the muscles on the left side are the ones usually paralyzed is owing to the difference in the anatomical arrangement of the nerves. The left nerve is much longer and more exposed to interference than the right nerve.

In chronic roaring there is no evidence of any disease of the larynx other than the wasted condition of the muscles in question. The disease of the nerve is generally far from the larynx. Disease of parts contiguous to the nerve along any part of its course may interfere with its proper function. Enlargement of lymphatic glands within the chest through which the nerve pa.s.ses on its way back to the larynx is the most frequent interruption of nervous supply, and consequently roaring. When roaring becomes confirmed, medical treatment is entirely useless, as it is impossible to restore the wasted muscle and at the same time remove the cause of the interruption of the nervous supply. Before roaring becomes permanent the condition may be benefited by a course of iodid of pota.s.sium, if caused by disease of the lymphatic glands. Electricity has been used with indifferent success. Blistering or firing over the larynx is, of course, not worthy of trial if the disease is due to interference of the nerve supply. The administration of strychnia (nux vomica) on the ground that it is a nerve tonic with the view of stimulating the affected muscles is treating only the result of the disease without considering the cause, and is therefore useless. The operation of extirpating the collapsed cartilage and vocal cord is believed to be the only relief, and, as this operation is critical and can be performed only by the skillful veterinarian, it will not be described here.

From the foregoing description of the disease it will be seen that the name "roaring," by which the disease is generally known, is only a symptom and not the disease. Chronic roaring is also in many cases accompanied with a cough. The best way to test whether a horse is a "roarer" is either to make him pull a load rapidly up a hill or over a sandy road or soft ground; or, if he is a saddle horse, gallop him up a hill or over soft ground. The object is to make him exert himself. Some horses require a great deal more exertion than others before the characteristic sound is emitted. The greater the distance he is forced, the more he will appear exhausted if he is a roarer; in bad cases the animal becomes utterly exhausted, the breathing is rapid and difficult, the nostrils dilate to the fullest extent, and the animal appears as if suffocation was imminent.

An animal that is a roarer should not be used for breeding purposes. The taint is transmissible in many instances.

_Grunting._--A common test used by veterinarians when examining "the wind" of a horse is to see if he is a "grunter." This is a sound emitted during expiration when the animal is suddenly moved, or startled, or struck at. If he grunts he is further tested for roaring. Grunters are not always roarers, but, as it is a common thing for a roarer to grunt, such an animal must be looked upon with suspicion until he is thoroughly tried by pulling a load or galloped up a hill. The test should be a severe one. Horses suffering with pleurisy, pleurodynia, or rheumatism, and other affections accompanied with much pain, will grunt when moved, or when the pain is aggravated, but grunting under these circ.u.mstances does not justify the term of "grunter" being applied to the horse, as the grunting ceases when the animal recovers from the disease that causes the pain.

_High blowing._--This term is applied to a noisy breathing made by some horses. It is distinctly a nasal sound, and must not be confounded with "roaring." The sound is produced by the action of the nostrils. It is a habit and not an unsoundness. Contrary to roaring, when the animal is put to severe exertion the sound ceases. An animal that emits this sound is called a "high blower." Some horses have naturally very narrow nasal openings, and they may emit sounds louder than usual in their breathing when exercised.

_Whistling_ is only one of the variations of the sound emitted by a horse called a "roarer," and therefore needs no further notice, except to remind the reader that a whistling sound may be produced during an attack of severe sore throat or inflammation of the larynx, which pa.s.ses away with the disease that causes it.

CHRONIC BRONCHITIS.

This may be due to the same causes as acute bronchitis or it may follow the latter disease. An attack of the chronic form is liable to be converted into acute bronchitis by a very slight cause. This chronic affection in most instances is a.s.sociated with thickening of the walls of the tubes. Its course is slower, it is less severe, and is not accompanied with so much fever as the acute form. If the animal is exerted, the breathing becomes quickened and he soon shows signs of exhaustion. In many instances the animal keeps up strength and appearances moderately well, but in other cases the appet.i.te is lost, flesh gradually disappears, and he becomes emaciated and debilitated. It is accompanied with a persistent cough, which in some cases is husky, smothered, or m.u.f.fled, while in others it is hard and clear. A whitish matter, which may be curdled, is discharged from the nose. If the ear is placed against the chest behind the shoulder blade, the rattle of the air pa.s.sing through the mucus can be heard within.

_Treatment._--Rest is necessary, as even under the most favorable circ.u.mstances a cure is difficult to effect. The animal can not stand exertion and should not be compelled to undergo it. It should have much the same general care and medical treatment prescribed for the acute form. a.r.s.enious acid in tonic doses (3 to 7 grains) three times daily may be given. As a.r.s.enic is irritant, it must be mixed with a considerable bulk of moist feed and never given alone. a.r.s.enic may be given in the form of Fowler's solution, 1 ounce three times daily in the drinking water. An application of mustard applied to the breast is a beneficial adjunct. The diet should be the most nourishing. Bulky feed should not be given. Linseed mashes, scalded oats, and, if in season, gra.s.s and green-blade fodder are the best diet.

THE LUNGS.

The lungs (see Pl. VII) are the essential organs of respiration. They consist of two (right and left) spongy ma.s.ses, commonly called the "lights," situated entirely within the thoracic cavity. On account of the s.p.a.ce taken up by the heart, the left lung is the smaller.

Externally, they are completely covered by the pleura. The structure of the lung consists of a light, soft, but very strong and remarkably elastic tissue, which can be torn only with difficulty. Each lung is divided into a certain number of lobes, which are subdivided into numberless lobules (little lobes). A little bronchial tube terminates in every one of these lobules. The little tube then divides into minute branches which open into the air cells (pulmonary vesicles) of the lungs. The air cells are little sacs having a diameter varying from one-seventieth to one two-hundredth of an inch; they have but one opening, the communication with the branches of the little bronchial tubes. Small blood vessels ramify in the walls of the air cells. The air cells are the consummation of the intricate structures forming the respiratory apparatus. They are of prime importance, all the rest being complementary. It is here that the exchange of gases takes place. As before stated, the walls of the cells are very thin; so, also, are the walls of the blood vessels. Through these walls escapes from the blood the carbonic acid gas that has been absorbed by the blood in its circulation through the different parts of the body; through these walls also the oxygen gas, which is the life-giving element of the atmosphere, is absorbed by the blood from the air in the air cells.

CONGESTION OF THE LUNGS.