Generic name for common symptom. Low and high notes. Grunter, roarer,
whistler, piper, highblower. Pace or effort develops. Causes: of
temporary roaring, inflammations, abscess, phlebitis, choking, dropsy,
petechial fever, phlegmons along vagus. Causes of inveterate roaring,
paresis of left recurrent laryngeal nerve, fatty degeneration of left
arytenoid muscles, fracture of facial bones, polypi in air passages,
chronic thickening of mucosa, foreign bodies in passages, tumors of
lymph glands, abscess of guttural pouches, pseudo membrane, laryngeal
ulceration, ossification, distortion, fracture of cartilages, action
of forcible inspiration, leading on left side, deep origin of
recurrent nerve, effect of chest diseases and violent heart action,
examples of morbid conditions impairing innervation. Lesions in
muscles, and nerves. Facial palsy, poison (chick vetch, winter vetch,
lead, fungi, moulds). Intermittent roaring. Hereditary roaring.
Symptoms, grunting when coughed or threatened, heavy draft, gallop,
noise, laryngeal tremor, cold as a complication, roaring with
expiration, lesions. Treatment, its use. Prevention, avoid breeding
roarers, bearing reins, chick vetch, lead. Tonic medication, caustic
to mucosa, firing, setons, iodine, pad nostrils, tracheotomy,
arytenectomy, electricity.
This is the name of a symptom rather than a disease. It implies a sound
made in breathing in connection with some contraction of the air
passages. The term is however usually reserved for those conditions in
which the sound results, from chronic disease or malformation, the noise
attendant on laryngitis and other acute diseases being rarely spoken of
as _roaring_. In neither case does the noise indicate more than that
there is some impediment to the ingress and egress of air through larynx
or trachea.
The pitch of the note varies exceedingly with the causes that produce it
and with the hurried nature of the breathing. There have thus arisen the
epithets of _grunter_, _roarer_, _whistler_, _highblower_, _piper_,
_trumpeter_, _wheezer_, _etc_. The most common distinctions are those of
_roaring_ and _whistling_. The _roarer_ produces a loud deep basso sound
in inspiration, the larynx or windpipe being only slightly narrowed
while the _whistler_ or _piper_ produces a shrill blowing or sibilant
noise because of the greater constriction of the passage. The term
_grunter_ is derived from the facts that a _roarer_ usually makes a
grunting noise when struck or threatened with a cane, and that when the
upper cartilages of the windpipe are pinched between the finger and the
thumb the resulting cough is prolonged and somewhat like a _grunt_. A
_wheezer_ is usually suffering from spasmodic contraction of the
bronchial tubes, from broken wind or from chronic bronchitis. A
_highblower_ should never be spoken of in the same connection, as the
noise is made from a playful flapping of the false nostrils or soft
palate and disappears when the animal is put to the top of his speed. It
is from confounding _high-blowing_ with _roaring_ that _Eclipse_ and
other brilliant performers on the English turf have been erroneously
pronounced _roarers_.
The noise produced by the _roarer_ is not heard while he stands quiet,
nor many cases even during a short trot or gallop. Such horses are in
consequence often sold at the hammer and the purchaser is grievously
disappointed to find that what he thought a sound horse is absolutely
useless for the purpose for which he designed it.
=Causes.= Before noticing the symptoms of roaring a consideration of the
causes will be useful to enable the reader the better to understand the
signs by which the different forms are manifested.
=Causes of temporary roaring.= Whatever impedes the current of air
causes roaring. Hence inflammatory diseases of the nose, throat,
windpipe or bronchial tubes; abscess of one or the other of these parts;
inflammation of a jugular vein and pressure on the trachea or vagus
nerve by the resulting swelling; choking; the swelling in the neck
consequent on the cutting open of the gullet for the relief of choking;
thickening of the nostrils from dropsy, loss of a jugular vein, purpura
hemorrhagica etc.; and swellings pressing on the vagus nerve, and which
may be situated at the base of the brain, in the neck or in the anterior
part of the chest. Also temporary infiltration of the laryngeal mucosa.
=Causes of inveterate roaring.= The one great cause of roaring and that
which sustains the disease in nineteen cases out of every twenty is
paralysis of the left _recurrent nerve_ of the larynx and wasting of
several of the arytenoid muscles on that side. It may be well, however,
first to notice the less frequent causes and wind up with this more
common one. 1st, Fracture with distortion of the nasal bones and
narrowing of the nasal passages (Gamgee). 2nd, Polypi and other tumors
of the nose, pharynx, larynx, windpipe or bronchi. 3rd, Chronic
thickening of the nasal mucous membrane, the result of inflammation.
4th, The presence of foreign bodies in the nose, as for example balls
coughed up from the pharynx. 5th, Hering records a case resulting from
the closure of the posterior opening of one nasal chamber by a membrane.
6th, Cancerous or melanotic deposits in the lymphatic glands above and
to each side of the pharynx and larynx. 7th, Distension of the guttural
pouches by inspissated pus. 8th, Chronic thickening of the mucous
membrane of the larynx consequent on inflammation. 9th, The formation of
a projecting fold of the mucous membrane or of a new production (false
membrane) in the windpipe as the result of inflammation. Such false
membranes have been known to become detached at their median part and
remain attached at their two extremities thus constituting a band
stretching from one side of the windpipe to the other. 10th, Ulceration
of the membrane of the larynx particularly on the projecting folds
circumscribing the glottis, 11th, Ossification of the laryngeal
cartilages and loss of their elasticity. 12th, Distortion of the
cartilages of the larynx, most commonly from unduly tight reining and
pulling the nose in toward the chest. In such cases the cartilages of
the larynx and those of the windpipe adjoining being compressed slide
within each other, and the enclosed edge projecting within the air tube
materially diminishes its calibre. 13th, Fracture of one or more rings
of the trachea. This usually results from blows, as in running the neck
against the back of a cart or wagon. The cartilaginous rings are usually
broken at their median part in front and being retained together by the
investing elastic tissue which enables the pieces to move on each other
as by a hinge, and being approximated by the contraction of the
trachealis muscle above, the ring is flattened from side to side and the
channel for the passage of air correspondingly decreased. This
flattening can be easily felt by the hand in the living horse. 14th, A
peculiar congenital distortion of the trachea caused by the curling in
of one end of each cartilage of the windpipe and the straightening out
of the other. This occasionally proceeds so far that the gullet is
lodged in the interspace overlapped and hidden by the free ends of the
cartilages, the diameter of the windpipe being proportionately
diminished. Distortions and fractures are usually overlooked by
veterinarians but from the frequency with which the author has met with
them in his dissection he is convinced that they deserve greater
attention than has been awarded them. 15th, Percivall records a case of
inveterate _roaring_ in which, even tracheotomy having failed to cure,
the patient was destroyed and the lungs found to be extensively
consolidated, many of the air tubes having been so compressed as to be
almost impervious. I have known a case of roaring from the presence of a
pedunculated tumor in the lower end of the windpipe where it divides to
enter the lungs, and the same result may ensue from the partial
obstruction of the bronchial tubes by masses of tenacious mucus in
chronic bronchitis.
16th. The immediate cause of _roaring_ in the immense majority of cases
is the =paralysis and fatty degeneration of certain muscles on the left
side of the larynx=. The muscles supplied with motive power by the =left
recurrent laryngeal nerve= (Crico-arytenoideus posticus,
Crico-arytenoideus lateralis, thyro-arytenoideus, and the left half of
the arytenoideus) are those constantly and exclusively affected, while
those supplied by the _superior laryngeal nerve_ (Crico-thyroideus,
hyo-thyroideus and hyo-epiglottideus) remain unchanged. The left
recurrent nerve is also wasted and considerably attenuated as compared
with that on the opposite side. The _modus operandi_ of this paralysis
and wasting in the production of _roaring_ is beautifully seen when the
upper part of the windpipe is laid open so as to expose the interior of
the larynx in laryngectomy. The triangular opening of the glottis is
seen fairly dilated while the muscles are relaxed in the act of
expiration. As soon, however, as inspiration commences the left
arytenoid cartilage slides completely into the passage, its lower border
projecting so much to the right that it forms a prominent crest
extending beyond the median line and in some cases closely approaching
the right wall of the larynx, the superior elastic and free border of
the same cartilage meanwhile gets drawn inward by the suction power of
the air so as to block up the passage still more. The closure of the
glottis being thus seen to be largely controlled by the current of
inspired air, it becomes evident that any increase in the force of the
current will aggravate it and a decrease will lessen the extent of the
closing and alleviate the distress of breathing. This fact furnishes a
means of palliating the symptoms. (See treatment.) It explains moreover
why roaring should not be heard in quiet breathing and why it should
increase in force and in pitch as the respiration becomes more and more
hurried. It further accounts for the noise being heard only during the
act of inspiration, the outward rush of the air in the expiratory act
being of itself sufficient to carry this valvular cartilage out of the
passage and secure a free and unimpeded current.
The paralysis and wasting of the left recurrent nerve and muscles are in
their turn due to very varied morbid states.
It may commence in the larynx from distortion of its cartilages and
inflammation of the mucosa, in which case the wasting of the nerve is
probably a result of its prolonged inactivity. This mode of origin is
strongly insisted on by Percivall, and no doubt occasionally arises.
Under this explanation, however, it is difficult satisfactorily to
account for its almost invariable occurrence on the left side. The mere
fact that the horse is habitually approached on this side and more
commonly turned toward it is a most insufficient reason.
Even if admitted it utterly fails to explain the immunity of the muscles
supplied by the superior laryngeal nerve.
The fact that a horse has usually a hard and soft side of the mouth and
carries the head slightly to the latter is no better explanation, as the
tender side is not always the left.
More commonly the disease arises at some other point near the origin or
in the course of the nerve, and the changes in the larynx follow as the
consequence of deficiency or entire absence of motor innervation. Many
cases can be cited in which such an origin was unquestionable, and on
the hypothesis that this is the true and constant history of the
development of the malady, its regular occurrence in the left side, and
the absence of all signs of wasting in the muscles supplied by the
superior laryngeal nerve are alike perfectly explainable.
Let it be noted that the vagus nerves (right and left) of which the
recurrent laryngeal are branches, originate from the base of the brain,
pass down the neck beneath the jugular vein in company with the carotid
artery; that on entering the chest the right vagus nerve gives off its
recurrent branch which proceeds at once up the neck along the course of
its parent trunk till it reaches the larynx, to the muscles on the right
side of which it is distributed; that the left vagus nerve on the other
hand proceeds backward in company with the left innominate artery as far
as the base of the heart, where on about the level of the space between
the sixth and seventh ribs it gives off the left recurrent nerve; that
this left recurrent nerve closely applied at its point of origin to the
great parent arteries turns round the posterior aorta enclosing it in a
loop, and gaining the lower end of the windpipe follows its course to
the larynx. It will thus be understood how many chest diseases may
implicate the left recurrent nerve, and from which the right, which
extends no deeper than between the two first ribs, may be completely
exempt. The frequent supervention of roaring as a sequel of chest
diseases receives in this an ample explanation. Its connection with
pleurisy becomes especially probable, as the nerve lies in contact with
the surface of the pleura alike in its descending and ascending course
within the chest.
Finally the loop encircling the posterior aorta exposes the nerve to
constant stretching and shocks from the heart’s action during violent
exertions and in excited states of the circulation generally. Vaerst and
Sussdorf show that the nerve is habitually flattened between the
posterior aorta and trachea, the effect being worst when the heart’s
action is excited.
It remains to notice a few instances in which dissection established the
connection of interference with the nerve at some part of its course and
the existence of roaring.
(a.) Godine found in a roarer a tumor about the size of a chicken’s egg,
pressing on the commencement of the pulmonary artery. He attributed the
roaring to the impaired circulation of blood in the lungs by the
pressure on the artery. Considering that the tumor must have been
precisely in the situation of the left recurrent nerve at its point of
origin, it becomes much more probable that the symptom resulted from
pressure on this nerve.
(b.) The elder Bouley found in one case a considerable engorgement of
the group of lymphatic glands in the anterior part of the chest and
through the centre of which the left recurrent nerve passed.
(c.) Fergusson of Dublin dissected a roarer in which he found besides
some tumors of the lymphatic glands in the pelvic and sublumbar regions,
an indurated and enlarged gland about four inches behind the anterior
opening of the thorax. The recurrent nerve between this and the larnyx
was wasted so that its fibres could scarcely be recognized, the
laryngeal muscles on that side were atrophied, and degenerated, and the
glottis distorted and partly closed. Fergusson has in his description
made the mistake of writing the _right_ for the _left_; it is evident
that the _right recurrent nerve_ could not possibly pass through a tumor
in the situation described.
(d.) Gamgee furnishes a drawing of an immense tumor filling up the
anterior part of the chest, pressing on the vagi and recurrent nerves
and causing roaring.
(e.) The Clinique of the Alfort Veterinary School furnishes the
following among other cases of roaring consequent on inflammation of the
jugular vein. A well-bred and very fast English thoroughbred had been
used for two years by his owner who was a hard rider. In June, 1857, he
was bled as a preventive (saignée de precaution), suppurative phlebitis
was induced and was only cured at the end of six weeks. When again put
to work he proved a _roarer_ and was still affected when seen six months
later.
In connection with this it may be noted that the swelling in connection
with the inflammation of the vein extends easily to the subjacent vagus
and recurrent nerves, leading to their inflammation, functional
inactivity and atrophy. Bleeding is usually done on the left side of the
neck so that the paralysis and wasting would still be on the same side.
Happily with a more humane system of treatment, accidents of this kind
are less frequent than formerly. Glöckner furnishes a case which
followed thrombosis of the carotid.
(f) Reynal reports several cases in which _roaring_ had occurred as a
sequel of inflammations and abscess about the throat, and in which
infiltrations or gray or yellow indurations had taken place in the
areolar tissue around the vagus nerve. As nothing is more common than to
find _roaring_ resulting from severe sore throat, parotitis, etc., this
may explain its occurrence.
Mandl first carefully examined the paralyzed muscles which present to
the naked eye a flattened and wasted appearance in marked contrast to
the full well-rounded forms or those on the opposite side. They differ
no less in color. In place of the deep red of the healthy muscles those
on the diseased side are of a yellowish white hue with here and there a
pink streak indicating the position of some unchanged muscular fibre.
When placed under the microscope the healthy elements of the muscular
fibres (sarcous elements) are seen to be replaced by granules of fat.
The nerve (recurrent) is not only visibly wasted but its internal white
substance (white substance of Schwann) can no longer be recognized and
it approximates closely in character to a filament of ordinary white
fibrous tissue.
17th. Muscular paralysis due to other causes and even located in
different parts has been known to give rise to _roaring_.
Goubaux and others have noted the occurrence of roaring from paralysis
of one nostril, alike when the loss of power was special to the nasal
muscles or common to all on one side of the face.
Roaring apparently from paralysis of the laryngeal muscles has been seen
frequently in animals fed on the seeds of leguminous plants and
specially of the _Lathyrus Cicera_ (_Lathyrus Sativus Stendel_). The
whole family of the _Leguminosæ_ is open to suspicion as occasionally
containing a poisonous principle capable of inducing paralysis in
animals fed on them. The _Lathyrus Sativus_ induces paralysis in man and
the domestic animals in some parts of India (Sleeman, Irving). The
common cultivated tare (Vicia Sativa) is well known to induce general
paralysis, commencing with the hind extremities, when fed to horses at
the period of ripening in Great Britain. In France the chick vetch
(Lathyrus Cicera or Sativa) has been repeatedly noticed to lead to the
development of roaring apparently from paralysis of the laryngeal
muscles. Horses fed on 17 lbs, daily (straw and seeds) were attacked
with roaring in five days. They gained in flesh and vigor, had a smooth
shining coat and supple skin, and standing at rest presented nothing
amiss, but after ten minutes trot they were seized with roaring and if
not stopped they soon fell to the ground, with symptoms of impending
suffocation, (Delafond). Horses fed heavily on the winter vetch with cut
hay and molasses were attacked with roaring if gently exercised for one
or two minutes. It came on suddenly and threatened instant suffocation.
One horse fell and lay half an hour in a frightful state of dyspnœa.
More commonly they recovered after a few minutes rest. In the intervals
no disturbance of breathing nor any change of appetite attested the
slightest deviation from health. Reynal, Cruzel, Caffin, Motte and
Ayrault mention similar occurrences.
The paralysis of chronic lead poisoning will also cause roaring.
=Occasional or intermittent roaring.= Puzzling cases are met with in
which a horse will _roar_ at one time and not at another. In such cases
the veterinary profession has incurred an amount of odium which was by
no means deserved. Two veterinarians, equally respectable and talented,
appearing in a Court of Justice to swear to the same animal which they
had examined on different days, respectively pronounce it a roarer or a
sound horse, as it happened to be at the time of the respective
examinations. Such cases have been differently accounted for.
Slight colds or _sore throats_ may cause roaring so long as they
persist. Tight reining with the nose drawn in toward the chest induces a
stridor in certain animals by distorting the larynx and trachea. Some
horses with thick necks, badly set on heads, and in a state of obesity,
roar, yet the symptom subsides when the superfluous fat is got rid of
and they are brought into hard working condition. Stallions are very
liable to make a noise from this cause. In a case of roaring which
disappeared when the horse had been exercised for some time Leblanc
diagnosed an œdema of the glottis which was absorbed under the increased
movement of the parts. He did not test his opinion by dissection.
=Roaring sometimes hereditary.= That roaring runs in families there can
be no doubt, but the direct cause appears to be mostly the transmission
of a faulty conformation. A head with faulty shape and badly set on; a
thick, short neck, deficient in mobility, or a small, narrow chest,
predisposed to acute diseases, descends from parents to offspring,
entailing a predisposition to roaring. The large Normandy horse is
notoriously subject to roaring, but then he is equally characterized by
a big, coarse head, narrow forehead and nostrils, big jowl, and narrow
intermaxillary space. In all breeds this form is very subject to
roaring, because of the stiffness of the neck and tendency to
compression of the larynx. With the head badly set on, as it is almost
of necessity in these animals, everything is done to produce roaring.
Not only is the head cruelly reined in at work, but the horse is kept a
great part of his time in the stable in the same or even in a worse
condition, the larynx meanwhile unnaturally compressed between his
narrow jaws and the nerve compressed or the larynx distorted.
It must be added, however, that like some other acquired distortions or
alterations roaring may repeat itself in the progeny. Goodwin mentions
an instance of it on the female side through three successive
generations of thoroughbreds. Of transmission on the side of the male
the following instance is noteworthy: M. Liphaert, an extensive
proprietor in Livonia, bought a first-class English thoroughbred
stallion. His progeny were healthy until he became a roarer at ten years
old. All his foals, got after this date, followed the sire in becoming
roarers, and, it is important to observe, almost all at the age of ten
years.
_Symptoms._ These, of course, are manifest enough while the animal is
sufficiently excited to give rise to the noise. Certain indications may
be obtained even while the animal stands in the stable. If _cough_ is
excited by pinching the upper rings of the windpipe it is prolonged into
a groan. If suddenly threatened with a cane the abrupt inspiration which
results is attended by a _grunt_. The absence of these symptoms is not,
however, sufficient to establish the nonexistence of roaring. The horse
must be galloped or put to heavy draught to fully test the breathing
organs. Galloping up a steep hill is perhaps the best test. A gallop
over a recently ploughed field is about equally good. Soft pasture land
or an unpaved road is preferable to Macadam or pavement. Galloping in a
riding school on the soft tan is an excellent measure as the sound is
confined and the animal is always within earshot of the examiner. The
person examining should either ride the horse himself or have a
disinterested party, in no way connected with either buyer or seller, to
mount him. If the rider is in the interest of the seller he may contrive
to slacken the pace before he reaches the examiner, or by irritating the
horse may make it difficult to approach him immediately on his being
pulled up. If in the interest of the buyer he may succeed, by the use of
a powerful bit, in drawing the horse’s nose in to the chest, or by
compressing the larynx with a tight throat latch he may produce noise in
breathing when the animal is suddenly brought to a stand. Unless the
course is up a steep hill or over a ploughed field the horse should be
galloped for from five to ten minutes; he should be then made to pass
close to the examiner at full speed, and finally brought up suddenly by
his side and without any previous slacking of his pace. The ear should
be at once placed close to the nostrils, when the slightest abnormal
sound accompanying the inspiratory act will be at once recognized.
Draught horses are sufficiently tested by driving them in a heavy
vehicle or one with the wheels dragged. By walking alongside or keeping
the ear near to the nostrils any harsh sound additional to the normal
blowing noise of hurried breathing is easily noted.
The finger placed on the larynx detects the strong vibratory tremor, and
Friedberger notes that the left arytenoid is much more easily displaced
than the right, increasing the stridor.
If the horse is, at the time of examination, the subject of a cold, sore
throat, or other acute disease of the air passages no importance is to
be attached to any noise made in breathing, but he cannot be pronounced
a _sound_ horse until, this malady having passed off, it is found on
careful examination that no such sequel has been left.
Among the most puzzling cases are those in which the roaring occurs with
periods of intermission. If the horse has been fed for a short time on
vetches this may account for its temporary access, and unless the same
feeding is again allowed a recurrence is not to be looked for. If due to
the occasional displacement of a pedunculated tumor of the nose or
pharynx and its interference with the action of the larynx its existence
may be recognized by careful examination, diminished current of air
through one nostril, etc. But there remain some _rare_ cases in which
there are no such appreciable causes, and yet the horse would be
pronounced _sound_ or _unsound_ as examined at certain intervals. On
this subject more information is desirable.
The following varieties of roaring will be distinguished from that
of paralysis by the occurrence of the sound in both acts of
breathing (expiration and inspiration):—distortions, tumors or
foreign bodies in the nose:—tumors about the throat, in the windpipe
or bronchi:—distortion of the windpipe, from tight reining, fracture
or congenital deformity:—and the presence of a false membrane
stretching across the windpipe.
Examination by manipulation, auscultation and percussion along the whole
length of the air passages alike during rest and after exercise, may
enable one in unusual cases to recognize the structural changes that
give rise to roaring.
_Treatment._ This has long been considered as hopeless, yet preservative
and palliative measures are usually accessible, whilst even cures can be
effected in certain conditions.
_Preventive treatment._ First may be noticed the rejection for breeding
purposes of all animals possessing those conformations of head, neck and
chest already referred to as conducing to disease of the air passages or
distortion of the larynx or windpipe. Equally ought all roarers to be
set aside unless the exciting cause is accidental such as fractures of
the nasal bones, of the trachea, the existence of polypi, etc. Stallions
that make a harsh noise in breathing from an accumulation of fat about
the throat are not necessarily objectionable.
The employment of the bearing rein so as to compress and distort the
larynx is to be avoided. If bearing reins are used in horses having
short thick necks and badly set on heads and especially with
intermaxillary narrowness they should be passed through rings in the
cheek piece of the bridle or between the ears and over the forehead
(overdraw check) so that while the head is elevated the nose may be
projected forward after the Russian fashion of equitation. This measure
has indeed appeared to cure several cases of roaring. I have met with
fewer roarers in the same number of horses in America than in England,
and this I attribute to the better mode of using the bearing rein on
this side of the Atlantic.
The Chick Vetch (Lathyrus Cicera) should be excluded from the fodder of
horses or used in small proportion only. In man it is found to be
injurious when it forms a twelfth part of the bread used and gives rise
to paralysis if it amounts to a third (Aitken).
_Palliative and Curative treatment._ Medicinal treatment will prove
useless in the great majority of cases: as for example in paralysis and
degeneration of the muscles, in ossifications, fractures, or distortions
of the cartilages, etc., etc. Nevertheless where there is merely
thickening of the membrane of the larynx alterative and tonic treatment
may be successful especially if associated with iodine ointment or
active blisters applied to the throat. A case is reported by Dupuy in
which a course of arsenic cured. In these cases as well as in those due
to ulceration of the membrane the application of caustic by means of a
staff and sponge as advised in laryngitis may prove beneficial. In some
cases of this kind the application of the firing iron to the region of
the larynx has an excellent effect. Setons have proved useful in some
cases.
In cases due to tumors or enlarged glands pressing on the air passages
the internal use of iodine and other alteratives and diuretics, and the
local applications of iodine, or mercurial ointments or of blisters have
been successful. Failing in this the tumors may be removed with the
knife when accessible.
If by auscultation the existence and position of a band of lymph can be
made out, tracheotomy may be performed and the band excised. Percivall
with reason doubts the possibility of the diagnosis.
In cases due to distortion of the larynx from tight reining the bearing
reins should be dispensed with or rearranged so as to encourage
protrusion of the nose, and the horse should be bitted to the side
chains or straps in the stall several hours daily so that the head shall
be elevated and the nose protruded.
When _roaring_ depends on paralysis of the laryngeal muscles, a mode of
palliation may be adopted as practised by the London omnibus and cab
men. A strap is fixed round the nose supported by a strap passing down
the middle of the face and the cheek piece of the bridle on each side
and buckled beneath the chin. On the inner side of this strap where it
passes over the false nostrils is attached on each side a semiovoid pad
which presses on the flap of the nostril and regulates the entrance of
air. The principle on which it acts will be understood when we consider
that the paralyzed cartilage is drawn into the passage by the rush of
air and that the closure of the channel is more complete and the roaring
more marked in proportion to the force of the current. The pads by
lessening and regulating the rush of air into the lungs thus leave the
passage in reality more open and largely obviate the difficulty of
breathing and the noise.
In extreme cases with the structural lesion in the head, throat, or
upper two-thirds of the neck relief may be secured by tracheotomy.
A more radical operation is that introduced by Günther for the excision
of the left arytenoid cartilage. As improved by Möller and others this
consists in an incision through the cricoid cartilage and crico-thyroid
membrane (or even the first rings of the trachea) and the complete
extirpation of the left arytenoid cartilage and left vocal cord. The
manipulations belong to surgery. The result is satisfactory in removing
the violent dyspnœa in hurried breathing and in very favorable cases in
obviating noise altogether. More commonly some stridor remains but not
enough to interfere with pace or with heavy draft. From my personal
experience in performing the operation, I would recommend it in all
cases in which the obstruction is so great as to interfere with the use
of the horse on the track, or road, or for heavy draught. But in slight
cases, in which the disease causes little or no inconvenience beside the
noise, I would advise some less radical measure.
Another obvious line of treatment is by the use of electricity locally
and of strychnine internally. A weak current kept up for fifteen minutes
may be sent from the positive pole in the left jugular furrow to the
negative pole over the left side of the larnyx. Strychnia in the dose of
two grains may be given daily in the food or in half that amount
hypodermically over the left side of the larnyx. This would be useful
only in the early stages with little or no fatty degeneration of the
muscles.