DISEASES OF THE RESPIRATORY APPARATUS
GENERAL DISCUSSION.--The respiratory apparatus may be divided into two
groups of organs, anterior and posterior. The anterior group, the
_nostrils, nasal cavities, pharynx, larynx_ and _trachea_, is situated in
the region of the head and neck. The posterior group, the _bronchial tubes_
and _lungs_, is situated in the chest or thoracic cavity.
_The nostrils_ are the anterior openings of the air passages. The nasal
cavities are situated in the anterior region of the head, and extend the
entire length of the face. Each cavity is divided into three long, narrow
passages by the two pairs of turbinated bones. The lining membrane is the
nasal mucous membrane, the lower two-thirds or respiratory portion
differing from the upper one-third, in that the latter possesses the nerve
endings of the olfactory nerve and is the seat of smell. The five pairs of
head sinuses communicate with the nasal cavities. Posteriorly and near the
superior extremity of the nasal passages, are two large openings, the
guttural, that open into the pharyngeal cavity.
_The pharynx_ is a somewhat funnel-shaped cavity. The walls are thin and
formed by muscles and mucous membrane. This is the cross-road between the
digestive and respiratory passages. In the posterior portion of the cavity
there are two openings. The inferior opening leads to the larynx and the
superior one to the oesophagus. All feed on its way to the stomach must
pass over the opening into the larynx. It is impossible, however, for the
feed to enter this opening, unless accidentally when the animal coughs. The
cartilage closing this opening is pressed shut by the base of the tongue
when the bolus of feed is passed back and into the oesophageal opening.
_The larynx_ may be compared to a box open at both ends. The several
cartilages that form it are united by ligaments. It is lined by a mucous
membrane. The posterior extremity is united to the first cartilaginous ring
of the trachea. The anterior opening is closed by the epiglottis. Just
within is a V-shaped opening that is limited laterally by the folds of the
laryngeal mucous membrane, the vocal chords.
_The trachea_ is a cylindrical tube originating at the posterior extremity
of the larynx, and terminating within the chest cavity at a point just
above the heart in the right and left bronchial tubes. It is formed by a
series of cartilaginous rings joined together at their borders by ligaments
and lined by a mucous membrane.
_The bronchial tubes_ resemble the trachea in structure. They enter the
lungs a short distance from their origin, where they subdivide into
branches and sub-branches, gradually decreasing in calibre and losing the
cartilaginous rings, ligaments and muscular layer until only the thin
mucous membrane is left. They become capillary in diameter, and finally
open into the infundibula of the air cells of the lungs.
_The lungs_ take up all of the space in the thoracic cavity not occupied by
the heart, blood-vessels and oesophagus. This cavity resembles a cone in
shape that is cut obliquely downwards and forward at its base. The base is
formed by the diaphragm which is pushed forward at its middle. It is lined
by the pleura, a serous membrane, that is inflected from the wall over the
different organs within the cavity. The median folds of the pleura divide
the cavity into right and left portions. A second method of describing the
arrangement of the pleura is to state that it forms two sacks, right and
left, that enclose the lungs. The lungs are the essential organs of
respiration. The tissue that forms them is light, will float in water, is
elastic and somewhat rose-colored. Each lung is divided into lobes, and
each lobe into a great number of lobules by the supporting connective
tissue. The lobule is the smallest division of the lung and is formed by
capillary bronchial tubes, air cells and blood-vessels. It is here that the
external respiration or the exchange of gases between the capillaries and
the air cells occurs.
VENTILATION.--It is agreed by all persons who have investigated the
subject, that unventilated stable air is injurious to animals. At one time
it was believed that the injurious effects resulting from the breathing of
air charged with gases and moisture from the expired air and the animal's
surroundings, were due to a deficiency in oxygen. It is now believed that
the ill-effects are mainly due to the stagnation of air, the humid
atmosphere, and the irritating gases emanating from the body excretions.
The common impurities found in _stable air_ are carbonic and ammonia gas,
moisture charged with injurious matter and dust from the floor and bodies
of the animals. As a rule, the more crowded and filthy the stable, the more
impurities there are in the air. If any of the animals are affected with an
infectious disease, such as tuberculosis or glanders, the moisture and dust
may act as carriers of the disease-producing germs. Infectious diseases
spread rapidly in crowded, poorly ventilated stables. The two factors
responsible for this rapid spread of disease are the lowered vitality of
the animal, due to breathing the vitiated air, and the greater opportunity
for infection, because of the comparatively large number of bacteria
present in the air.
_The purpose of stable ventilation_ is to replace the stable air with purer
air. The frequency with which the air in the stable should be changed
depends on the cubic feet of air space provided for each animal, and the
sanitary conditions present. The principal factor in stable ventilation is
the force of the wind. In cold weather it is very difficult to properly
ventilate a crowded stable without too much loss of animal heat and
creating draughts.
For practical purposes, the _need of ventilation_ in a stable can be
determined by the odor of the air, the amount of moisture present and the
temperature. It is impossible to keep the air within the stable as pure as
the atmosphere outside.
All dangers from injury by breathing impure air, or by draughts can be
eliminated by proper stable construction, attention to the ventilation and
keeping the quarters clean.
[Illustration: FIG. 22.--A case of catarrhal cold.]
CATARRH (COLD IN THE HEAD).--Catarrh is an inflammation of the mucous
membrane lining the nasal cavities that usually extends to the membrane
lining of the sinuses of the head. It may be acute or chronic. The
inflammation very often extends to the pharynx and larynx. Cold in the head
is more common in the horse than in any of the other animals (Fig. 22).
_The most common causes_ of "colds" are standing or lying in a draught,
becoming wet, and exposure to the cold. "Colds" are common during cold,
changeable weather. Horses that are accustomed to warm stables, are very
apt to take "cold" if changed to a cold stable and not protected with a
blanket. Most animals are not affected by the cold weather if given dry
quarters and a dry bed. Irritation to the mucous membrane by dust, gases
and germs is a common cause. Influenza and colt distemper are characterized
by an inflammation of the respiratory mucous membranes. In the horse,
chronic catarrh is commonly caused by diseased teeth, and injuries to the
wall of the maxillary sinus. In sheep, the larvae of the bot-fly may cause
catarrh.
_The early symptoms_ usually pass unnoticed by the attendant. The lining
membrane of the nostrils is at first dry and red. During this stage
sneezing is common. In a few days a discharge appears. This is watery at
first, but may become catarrhal, heavy, mucous-like and turbid. In severe
cases it resembles pus. The lining membrane of the eyelids appears red and
tears may flow from the eye. Sometimes the animal acts dull and feverish,
but this symptom does not last longer than one or two days unless
complicated by sore throat.
_Inflammation of the throat_ is a common complication of "colds." It is
characterized by difficulty in swallowing and partial, or complete loss of
appetite. Drinking or exercising causes the animal to cough. If the larynx
as well as the pharynx is inflamed, distressed and noisy breathing may
occur. Pressure over the region of the throat causes the animal pain.
Common "cold" terminates favorably within a week. Chronic catarrh may
persist until the cause is removed and the necessary local treatment
applied. Inflammation of the pharynx and larynx may persist for several
weeks unless properly treated. Abscesses may form in the region of the
throat. Horses frequently become thick winded as a result of severe attacks
of sore throat.
_The treatment_ is both preventive and curative. "Colds" and sore throat
can be largely prevented by good care, exercise and properly ventilated
stables. Mild cases require a light diet, comfortable quarters and a dry
bed. Allowing the animal to inhale steam three or four times daily is
useful in relieving the inflammation. Easily digested feeds, and in case
the animal has difficulty in swallowing, soft feeds and gruels, should be
given. The throat may be kept covered with a layer of antiphlogistin and
bandaged. Glycoheroin may be given in from teaspoonful to tablespoonful
doses, depending on the size of the animal. Chlorate of potassium may be
given in the drinking water.
If the animal becomes run down in flesh, as sometimes occurs in chronic
catarrh, bitter tonics should be given. In the latter disease, it is
sometimes necessary to trephine and wash out the sinus or sinuses affected
with an antiseptic solution. It may be necessary to continue this treatment
for several weeks.
BRONCHITIS.--Inflammation of the bronchial tubes may be either acute or
chronic. Acute bronchitis is especially common in the horse, while the
chronic form is more often met with in the smaller animals, especially
hogs. This disease is most common among horses during the changeable
seasons of the years. It is _caused_ by warm, close stables or stalls, and
irritating gases emanating from the floor, or manure in the stall. In
general, the causes are about the same as in cold in the head. In young
animals and hogs, the inhalation of dust, and bronchial and lung worms
commonly cause it. Verminous bronchitis usually becomes chronic.
_In the acute form_ of the disease the _symptoms_ come on very quickly, the
fever is high and the pulse beats and respirations are rapid. Chilling of
the body occurs, and the animal may appear dull and refuse to eat. The
animal coughs frequently. Recovery occurs within a few days, unless
complicated by sore throat and pneumonia. In the horse, bronchitis is not a
serious disease, but in other animals recovery is delayed and complications
are more common.
_In chronic bronchitis_ in the horse, the animal coughs frequently, there
is more or less discharge from the nostrils and the respirations may become
labored when exercised. The animal is usually weak, in poor flesh and unfit
for work. In other cases, symptoms of broken wind are noticed. Severe
coughing spells on getting up from the bed, or on moving about are
characteristic of bronchitis in hogs. Verminous bronchitis in calves and
lambs is characterized by severe spells of coughing, difficult and labored
breathing and a weak, emaciated condition.
_The preventive treatment_ is the same as for "colds." In the acute form
the treatment consists largely in careful nursing. Properly ventilated,
clean quarters that are free from dust should be provided. The animal
should be covered with a light or heavy blanket, depending on the
temperature of the stable, and the limbs bandaged. A light diet should be
fed for a few days. It is advisable to give the animal a physic of oil. The
inhalation of steam every few hours during the first few days should be
practised. Glycoheroin may be given three or four times a day.
Animals affected with chronic bronchitis should not be exercised or worked.
We should guard against their taking cold, give nourishing feeds, and a
tonic if necessary.
CONGESTION OF THE LUNGS.--Pulmonary congestion is generally due to
overexertion and exposure to extreme heat or cold. It may occur if the
animal is exercised when sick or exhausted. Hogs that are heated from
exercise and allowed access to cold water, may suffer from a congestion or
engorgement of the lungs. It may be present at the beginning of an attack
of pneumonia or pleurisy.
_The symptoms_ are difficult breathing and the animal fights for its
breath. The body temperature may be several degrees above the normal. In
the mild form, the above symptoms are not so marked. The onset and course
of the disease are rapid, recovery, pneumonia, or death often occurring
within twenty-four hours.
_Pulmonary haemorrhage_ is not uncommon. The discharge from the nostrils
may be slightly tinged with blood, or there may be an intermittent
discharge of blood from the nostrils or mouth. The mucous membranes are
pale, the animal trembles and shows marked dyspnoea.
_The preventive treatment_ consists in using the proper judgment in caring
for, and in working or exercising animals. This is especially true if the
animal is affected with acute or chronic disease. At the very beginning,
bleeding should be practised. Hot blankets renewed frequently and bandages
to the limbs is a very necessary part of the treatment. In case of severe
pulmonary haemorrhage, treatment is of little use.
PNEUMONIA.--Inflammation of the lungs is more common in horses than in any
of the other domestic animals. The croupous form is the most common. The
inflammation may affect one or both lungs, one or more lobes, or scattered
lobules of lung tissue. The inflammation may be acute, subacute or chronic.
_The causes_ are very much the same as in other respiratory diseases.
Exposure to cold and wet, stable draughts, becoming chilled after
perspiring freely and washing the animal with cold water are the common
causes of pneumonia. Inflammation of the lungs is especially apt to occur
if the animal is not accustomed to such exposure. Animals affected with
other respiratory diseases are predisposed to pneumonia. Drenching animals
by way of the nostril and irritating drenches, or regurgitated feed passing
into the air passages and lungs are the traumatic causes of pneumonia.
_The symptoms_ vary in the different forms of pneumonia. In case pneumonia
occurs secondarily, the earliest symptoms are confounded with those of the
primary disease. The first symptoms noticed may be a high body temperature,
as indicated by chills, and refusing to eat. The visible mucous membranes
are red and congested, the nostrils dilated, the respirations quickened and
difficult, the expired air hot and the pulse beats accelerated. The animal
coughs, and in the horse, a rusty discharge may be noticed adhering to the
margins of the nostrils. The horse refuses to lie down if both lungs are
inflamed. In severe cases the expression of the face indicates pain, the
respirations are labored, the general symptoms aggravated, and the animal
stands with the front feet spread apart. Cattle are inclined to lie down,
unless the lungs are seriously affected. Hogs like to burrow under the
litter.
_The course of croupous pneumonia_ is typical, and unless it terminates
fatally in the first stage, the periods of congestion, hepatization and
resolution follow each other in regular manner. Auscultation of the lungs
is of great value in diagnosing and watching the progress of the disease.
It is more difficult to determine the character of the lung sounds in the
horse and cow than it is in the small animals. This is especially difficult
if the animal is fat. During the period of _congestion_ which lasts about a
day, one can hear both healthy and crepitating sounds. The period of
_hepatization_ is characterized by an absence of sound over the diseased
area. The inflammatory exudates become organized at the beginning of this
stage, and the air can not enter the air cells. This period lasts several
days. _Resolution_ marks the beginning of recovery or convalescence. Toward
the end of the second period, the inflammatory exudate in the air cells has
begun to degenerate. In the last stage, these exudates undergo liquefaction
and are absorbed, or expelled by coughing, in from seven days to two weeks,
depending on the extent of the inflammation and the general condition of
the animal.
_In the subacute form_ the symptoms are mild and may subside within a week.
Sometimes _abscesses_ form in the lung. _Gangrenous inflammation_ of the
lung can be recognized by the odor of the expired air and the severity of
the symptoms. This form of pneumonia terminates fatally. If the larger
portion of the lung tissue is inflamed, death from asphyxia may occur in
the second stage.
The success in the _treatment_ of pneumonia depends largely on the care.
Properly ventilated, clean, comfortable quarters and careful nursing are
highly important. Large animals should be given a roomy box stall. Cold
does not aggravate pneumonia, providing the animal's body is well protected
with blankets and the limbs bandaged. Wet, damp quarters and draughts are
injurious. Hogs should be given plenty of bedding to burrow in. A light,
easily digested diet should be fed. Very little roughage should be fed. If
the animal does not eat well, it may be given eggs and milk. Weak pulse
beats should be treated by giving digitalis and strychnine.
Counterirritation to the chest wall is indicated. During convalescence,
bitter tonics may be given. Constipation should be treated by giving the
animal castor or linseed oil.
PLEURISY.--Inflammation of the pleura is most common in horses. It occurs
in all farm animals and is frequently unilateral. There are two forms of
pleurisy, acute and chronic. Pleuropneumonia is common when the cause is a
specific germ. This occurs in tuberculosis, pleuropneumonia of horses and
pneumococcus infection.
_The common causes_ are exposure to cold, chilling winds, draughty, damp
quarters, and drinking cold water when perspiring. Injuries to the costal
pleura by fractured ribs and punctured wounds may cause it to become
inflamed.
The early symptoms of acute pleurisy are chills, rise in body temperature,
pain and abdominal breathing. The most characteristic symptom is the ridge
extending along the lower extremities of the ribs (pleuritic ridge). The
animal does not stand still as in pneumonia, but changes its position
occasionally, its movements in many cases being accompanied by a grunt.
Pressure on the wall of the chest causes the animal to flinch and show
evidence of severe pain. Large animals rarely lie down. The cough is short
and painful. On placing the ear against the wall of the chest and listening
to the respirations, we are able to hear friction sounds. After a few days
effusion occurs in the pleural cavity. Although the animal may have refused
to eat up to this time, it now appears greatly relieved and may offer to
eat its feed. This relief may be only temporary. If the fluid exudate forms
in sufficient quantity to cause pressure on the heart and lungs and
interfere with their movement, the pulse beat is weak, the respirations
quick and labored, the elbows are turned out and the feet are spread apart.
All of the respiratory muscles may be used. The expression of the face may
indicate threatened asphyxia. We may determine the extent of the pleural
exudate by auscultation. There is no evidence of respiratory sounds in that
portion of the chest below the surface of the fluid. Dropsical swellings
may occur on the under surface of the breast and abdomen.
_In subacute cases_ evidence of recovery is noted in from four to ten days.
_Acute pleurisy_ very often terminates fatally. Under the most favorable
conditions, recovery takes place very slowly, sometimes extending over a
period of several months. It is not uncommon for the horse to continue
having "defective wind."
_The treatment_ consists in good care, well ventilated quarters and careful
nursing, the same as recommended in the treatment of pneumonia. At the very
beginning, the pain may be relieved by the administration of small doses of
morphine. If the conditions in the stable permit, a hot blanket that has
been dipped in hot water and wrung out as dry as possible, may be applied
to the chest wall and covered with a rubber blanket. This treatment should
be continued during the first few days of the inflammation. These
applications may be reinforced by occasionally applying mustard paste to
the sides of the chest.
The animal should be allowed to drink but a limited amount of water. The
feed must be highly nutritious. Milk and eggs should be given if necessary.
A laxative dose of oil should be given. Calomel, aloes, and digitalis are
recommended when the effusion period approaches in order to increase the
elimination of fluid, and lessen its entrance into the body cavity. If the
amount of effusion is large, puncture of the thoracic cavity with a trocar
and cannula may be practised. This operation should be performed carefully,
and all possible precautions used against infection of the wound. During
the later period of the disease iodide of potassium, iron and bitter tonics
should be given.
BROKEN-WIND, HEAVES.--The terms broken-wind and heaves are used in a way to
include a number of different diseases of the respiratory organs of the
horse. The term heaves is applied almost wholly to an emphysematous
condition of the lungs. Broken-wind may include the following diseased
conditions: obstruction of the nasal passages by bony enlargements and
tumors; tumors in the pharynx; enlarged neck glands; collection of pus in
the guttural pouches and paralysis of the left, or both recurrent nerves
(roaring).
_The common causes_ of heaves are pre-existing diseases of the respiratory
organs, severe exercise when the animal is not in condition and wrong
methods of feeding. Heaves is more common in horses that are fed heavily on
dusty timothy and clover hay and allowed to drink large quantities of water
after feeding, than in horses that are fed green feeds, graze on pastures
or receive prairie hay for roughage. Chronic indigestion seems to aggravate
the disease. Over-distention of the stomach and intestines due to feeding
too much roughage and grain interferes with respiration. Severe exercise
when in this condition may result in over-distention, dilation and rupture
of the air cells. This is the most common structural change met with in the
lungs of horses affected with heaves. It is termed emphysema.
_The common symptoms_ noted are the double contraction of the muscles of
the flank with each expiration, a short, dry cough and the dilated
nostrils. The frequent passage of gas is a prominent symptom in
well-established cases of heaves. Chronic indigestion is commonly present
in heavy horses that are not well cared for, or are given hard work. This
condition aggravates the distressed breathing.
Heaves is a permanent disorder, but it may be relieved by climatic changes
and careful attention to the animal's diet.
The following _preventive treatment_ is recommended: Dusty hay should not
be fed to horses. Clover hay is not a safe feed for horses that are worked
hard. When starting on a drive after feeding, the horse should not be
driven fast, but allowed to go slowly for a few miles.
The symptoms can be greatly relieved by careful attention to the diet. A
limited quantity of roughage should be fed, and this should be good in
quality and fed in the evening. During the warm weather, the animal should
be watered frequently. After quitting work in the evening the animal may be
allowed to drink as much water as it wants. Plenty of grain, soft feed and
roots may be fed. A small handful of flaxseed meal given with the feed
helps in keeping down constipation. Fowler's solution of arsenic may be
given twice daily with the feed, in half-ounce doses for a period of ten
days or two weeks. Chronic indigestion should be combated by digestive
tonics.
QUESTIONS
1. Name the organs that form the anterior and posterior air passages.
2. To what conditions are the injurious effects of keeping animals in a
poorly ventilated stable due?
3. State the purpose of ventilation. How can the need of ventilation be
determined in a stable?
4. State the causes of "cold" in the head; give the treatment.
5. State the cause of bronchitis; give the treatment.
6. What are the causes of pneumonia? Describe the symptoms and treatment.
7. What symptoms are characteristic of pleurisy? Give the treatment for
pleurisy.
8. Give the causes and treatment of "heaves."