excessive excitement is followed by an almost complete exhaustion of the
functional activity of the laminated tissues, the exhaustion by
congestion, and eventually by inflammation. But congestion here, as in
all other tissues, is not necessarily followed by inflammation; for,
although the principal symptoms belonging to true laminitis are present,
the congestion may be relieved before the processes of inflammation are
fully established. This is the condition in the many so-called cases of
laminitis which recover in from 24 to 48 hours. They should be called
congestion of the laminae.
Laminitis from concussion is common in trotting horses that are raced
when not in condition, especially if they carry the obnoxious toe
weights, and in green horses put to work on city pavements to which they
are unaccustomed. Concussion from long drives on dirt roads is at times
productive of the same results, notably when the weather is extremely
warm, or at least when the relative change of temperature is great. But
the exhaustion of these circumstances must prove an exciting cause as
well as the long-continued concussion. This combination of causes must
also determine the disease at times in hunters, for the weight of the
rider increases the demands made upon the function of these tissues, and
their powers are the sooner exhausted.
(2) Overexertion, as heavy pulling or rapid work, even when there is no
immoderate concussion, occasionally results in this disease. Here also
exhaustion is a conjunctive cause, for overexertion can not be long
continued without exhaustion.
(3) Exhaustion is nearly as prolific a source of laminitis as is
concussion, for when the physical strength is impaired, even though
temporarily, some part of the economy is rendered more vulnerable to
disease than others. To this cause we must ascribe those cases which
follow a hard day's work, in which at no time has there been
overexertion or immoderate concussion.
The tendency to laminitis in horses on sea voyages results from the
continual constrained position the animal maintains on account of the
rocking motion of the vessel.
If one foot has been blistered, or if one limb is incapacitated from any
cause, the opposite member, doing double duty, soon becomes exhausted,
and congestion, followed by inflammation, results. When one foot only
becomes laminitic, it is customary to find the corresponding member
participating at a later date; not always because of sympathy, but
because one foot had to do the work of two.
(4) Rapid changes of temperature act as an exciting cause of laminitis
by impairing the normal blood supply.
This change of temperature may be induced by drinking large quantities
of cold water while in an overheated condition. Here the internal heat
is rapidly reduced, the neighboring tissues and blood vessels
constrained, and the blood supply to these organs greatly diminished,
while the quantity sent to the surface is correspondingly increased.
True, in many cases there has not been sufficient labor performed to
impair the powers of the laminae, and laminitis is more readily induced
than congestion or inflammation of the skin or other surface organs,
because the laminae can not relieve themselves of threatened congestion
by the general safety valve of perspiration. A cold wind or relatively
cold air allowed to play upon the body when heated and wet with sweat
has virtually the same result, for it arrests evaporation and rapidly
cools the external surface, thereby determining an excess of blood to
such organs and tissues as are protected from this outside influence. In
many instances this happens to be some of the internal organs, as the
lungs, if the previous work has been rapid and their functional activity
impaired; but in numerous other instances the determination is toward
the feet, and that it is so depends upon two very palpable facts: First,
that these tissues have been greatly excited and are already receiving
as much blood as they can accommodate consistently with health; second,
even though these tissues are classed with those of the surface, their
protection from atmospheric influences by means of the thick box of horn
incasing them renders them in this respect equivalent to internal
organs.
A more limited local action of cold may excite this disease, by driving
through water or washing the feet and legs while the animal is warm or
just in from work. Here a very marked reaction takes place in the
surface tissues of the limbs, and passive congestion of the foot results
from an interference with the return flow of blood which is being sent
to these organs in excess. These are more liable to be simple cases of
congestion, soon to recover, yet they may become true cases of
laminitis.
(5) Why it is that certain kinds of grain will cause laminitis does not
seem to be clearly understood. Certainly they possess no specific action
upon the laminae, for all animals are not alike affected; neither do they
always produce these results in the same animal. Some of these feeds
cause a strong tendency to indigestion, and the consequent irritation of
the alimentary canal may be so great as to warrant the belief that the
laminae are affected through sympathy. In other instances there is no
apparent interference with digestion nor evidence of any irritation of
the mucous membranes, yet the disease is in some manner dependent upon
the feed for its inception. Barley, wheat, and sometimes corn are the
grains most liable to cause this disease. With some horses there appears
to be a particular susceptibility to this influence of corn, and the use
of this grain is followed by inflammation of the feet, lasting from a
few days to two weeks. In these animals, to all appearances healthy, the
corn neither induces colic, indigestion, nor purging, and apparently no
irritation whatever of the alimentary canal.
(6) Fortunately purgative medicines rarely cause inflammation of the
laminae. That it is, then, the result of sympathetic action is no doubt
more than hypothetical, for when there is no derangement of the
alimentary canal a dose of cathartic medicine will at times bring on
severe laminitis.
(7) Almost all the older authorities were agreed that metastatic
laminitis is a reality. In my opinion metastatic laminitis is nothing
more nor less than concurrent laminitis, and presents little in any way
peculiar outside the imperfectly understood exciting cause. The
practitioner who allows the acute symptoms of the laminitis to mislead
him, simply because their severity has overshadowed those of the primary
disease, may lose his case through unguarded subsequent treatment. This
form of laminitis is by no means commonly met with. It may be found in
conjunction with pneumonia, according to Youatt with inflammation of the
bowels and eyes, and according to Law and Williams sometimes with
bronchitis.
_Symptoms._--Laminitis is characterized by a congregation of symptoms so
well marked as scarcely to be misinterpreted by the most casual
observer. They are nearly constant in their manifestations, modified by
the number of feet affected, the cause which has induced the disease,
the previous condition of the patient, and the various other influences
which to some extent operate in all diseases. They may be divided into
general symptoms, which are concomitants of all cases of the disease,
subject to variations in degree only, and special symptoms, or those
which serve to determine the feet affected and the complications which
may arise.
_General symptoms._--Usually, the first symptom is the interference with
locomotion. Occasionally the other symptoms are presented first. As the
lameness develops the pulse becomes accelerated, full, hard, and strikes
the finger strongly; the temperature soon rises several degrees above
the normal, reaching sometimes 106 deg. F.; it generally ranges between
102.5 deg. and 105 deg. F. The respirations are rapid and panting in character,
the nostrils widely dilated, and the mucous membranes highly injected.
The facial expression is anxious and indicative of the most acute
suffering, while the body is more or less bedewed with sweat. At first
there may be a tendency to diarrhea, or it may appear later as the
result of the medicines used. The urine is high colored, scant in
quantity, and of increased specific gravity, owing to the water being
eliminated by the skin instead of the kidneys. The appetite is impaired,
sometimes entirely lost, but thirst is greatly increased. The affected
feet are hot and dry, and as much as possible are relieved from bearing
weight. Rapping them with a hammer, or compelling the animal to stand
upon one affected member, causes intense pain. The artery at the fetlock
throbs beneath the finger.
_Special symptoms._--Liability to affection varies in the different feet
according to the exciting cause. Any one or more of the feet may become
the subject of this disease, although it appears more often in the fore
feet than in the hind ones. This is due to the difference of the
function, i. e., that the fore feet are the bases of the columns of
support, receiving nearly all the body weight during progression and
consequently most of the concussion, while the hind feet become simply
the fulcra of the levers of progression, and are almost exempt from
concussion.
_One foot._--Injuries and excessive functional performance are the
causes of the disease in only one foot. The general symptoms, as a rule,
are not severe, there being often no loss of appetite and no unusual
thirst, while the pulse, temperature, and respiration remain about
normal. The weight of the body is early thrown upon the opposite foot,
and the affected one is extended, repeatedly raised from the floor, and
then carefully replaced. When made to move forward the lame foot is
either carried in the air while progression is accomplished by hopping
with the healthy one, or else the heel of the first is placed upon the
ground and receives little weight while the sound limb is quickly
advanced. Progression in a straight line is more easy than turning
toward the lame side.
_Both fore feet._--When both fore feet are affected the symptoms are
well marked. The lameness is excessive and the animal almost immovable.
When standing the head hangs low down, or rests upon the manger as a
means of support and to relieve the feet; the fore feet are well
extended so that the weight is thrown upon the heels, where the tissues
are least sensitive, least inflamed, and most capable of relief by free
effusion. The hind feet are brought forward beneath the body to receive
as much weight as possible, thereby relieving the diseased ones. If
progression is attempted, which rarely happens voluntarily during the
first three or four days, it is accomplished with very great pain and
lameness at the starting, which usually subsides to an extent after a
few minutes' exercise. During this exercise, if the animal happens to
step upon a small stone or other hard substance, he stumbles painfully
and is excessively lame in the offended member for a number of steps,
owing to the acute pain which pressure upon the sole causes in the
tissues beneath. The manner of the progression is pathognomonic of the
complaint. Sometimes the affected feet are simultaneously raised from
the ground (the hind ones sustaining the weight), then advanced a short
distance and carefully replaced; at almost the same moment the hind ones
are quickly shuffled forward near to the center of gravitation.
In other instances one foot at a time is advanced and placed with the
heel upon the ground in the same careful manner, all causes of
concussion being carefully avoided. In attempting to back the animal he
is found to be almost stationary, simply swaying the body backward on
the haunches and elevating the toes of the diseased feet as they rest
upon their heels. In attempting to turn either to the right or left he
allows his head to be drawn to the one side to its full extent before
moving, then makes his hind feet the axis around which the forward ones
describe a shuffling circle.
In most of cases of laminitis in the fore feet the animal persists in
standing until he is nearly recovered. In other cases he as persistently
lies, standing only when necessity seems to compel it, and then for as
short a time as possible. If the recumbent position is once assumed, the
relief experienced tempts the patient to seek it again; so we often find
him down a greater part of the time. But this is not true of all cases;
sometimes he will make the experiment, then cautiously guard against a
repetition. Even in cases of enforced recumbency, he ofttimes takes
advantage of the first opportunity and gets upon his feet, doggedly
remaining there until again laid upon his side. How to explain this
diversity of action I do not know; theoretically the recumbent position
is the only appropriate one, except when complications exist, and the
one which should give the most comfort, yet it is rejected by very many
patients and, no doubt, for some good reason. It has been suggested as
an explanation that when the animal gets upon his feet after lying for a
time the suffering is so greatly augmented that the memory of this
experience deters him from an attempted repetition. If this were true,
the horse with the first attack must necessarily make the experiment
before knowing the after effects of lying down, yet many remain standing
without even an attempt at gaining this experimental knowledge.
The most-favored position of the animal when down is on the broadside,
with the feet and legs extended. While in this position the general
symptoms greatly subside; the respirations and pulse become almost
normal; the temperature falls and the perspiration dries. It is with
difficulty that he is made to rise. When he attempts it he gets up
rapidly and "all of a heap," as it were, shifting quickly from one to
the other foot until they become accustomed to the weight thrown upon
them. Occasionally a patient will get up like a cow, rising upon the
hind feet first. Although enforced exercise relieves the soreness to
some extent, it is but temporary, for after a few minutes' rest it
returns with all its former severity.
_Both hind feet._--When only both hind feet are affected, they are,
while standing, maintained in the same position as when only the fore
ones are the subjects of the disease, but with an entirely different
object in view. Instead of being there to receive weight, they are so
advanced that the heels only may receive what little weight is
necessarily imposed on them; the fore feet at the same time are placed
well back beneath the body, where they become the main supports; the
animal standing, as Williams describes it, "all of a heap."
Progression is even more difficult now than when the disease is confined
to the anterior extremities. The fore feet are dubiously advanced a
short distance and the hind ones brought forward with a sort of kangaroo
hop that results in an apparent loss of equilibrium which the animal is
a few moments in regaining. The general symptoms, or, in other words,
the degree of suffering, seem more severe than when the disease affects
the fore feet alone. The standing position is not often maintained, the
patient seeking relief in recumbency. This fact is easily understood
when we consider how cramped and unnatural is the position he assumes
while standing and, if it were maintained for any considerable length of
time, would, no doubt, excite the disease in the fore feet, as explained
by D'Arboval.
_All four feet._--Laminitis of all four feet is but uncommonly met with.
The author has seen but three such cases. In all these the position
assumed was nearly normal. All the feet were slightly advanced, and
first one, then another, momentarily raised from the ground and
carefully replaced, this action being kept up almost continually during
the time the animal remained standing. The suffering is most acute, the
appetite lost, and, although the patient lies most of the time, the
temperature remains too high. The pulse and respirations are greatly
accelerated, the body covered with sweat, and bed sores are unpleasant
accompaniments.
_Course._--The course which laminitis takes varies greatly in different
cases, being influenced more or less by the exciting cause, the animal's
previous condition, the acuteness of the attack, and the subsequent
treatment. The first symptoms rarely exhibit themselves while the animal
is at his work, although we occasionally see the gait impaired by
stumbling, the body covered with a profuse sweat, and the respirations
become blowing in character as premonitions of the oncoming disease;
but, as a rule, nothing amiss with the animal is noted until he has
stood for some time after coming in from work, when, in attempting to
move him, he is found very stiff. Like all congestions, the early
symptoms usually develop rapidly; yet this is not always the case, for
often there appears to be no well-defined period of congestion, the
disease seemingly commencing at a point and gradually spreading until a
large territory is involved in the morbid process.
_Simple congestion._--Those cases of simple congestion of the laminae,
which we erroneously call laminitis, are rapidly developed, the symptoms
are but moderately severe, and but one to three days are required for
recovery. There are no structural changes and but a moderate exudate.
This is rapidly reabsorbed, leaving the parts in the same condition as
they were previous to the attack. If the congestion has been excessive,
a rupture of some of the capillaries will be found, a condition more
liable to exist if the animal is made to continue work after a
development of symptoms has begun.
True, the majority of these last-described cases prove to be the
laminitis in fact, yet the congestion may pass away and the extravasated
blood be absorbed without inflammation sufficient to warrant calling it
laminitis. The seat of greatest congestion will always be found in the
neighborhood of the toe, because of the increased vascularity of that
part, and, although at times it is limited to the podophyllous tissue
alone, any or all parts of the keratogenous membrane may be affected by
the congestion and followed finally by inflammation.
_Acute._--In the acute form of laminitis the symptoms may all develop
rapidly, or it may commence by the appearance of a little soreness of
the feet which in 24 or 48 hours develops into a well-marked case. This
peculiarity of development is due to one of two causes. Either the
congestion is general, but takes place slowly, or it begins in one or
more points and gradually spreads throughout the laminae. These acute
cases generally run their course in from one to two weeks. Usually a
culmination of the symptoms is reached, if the patient is properly
treated, in from three to five days; then evidences of recovery are
discernible in favorable cases. The lameness improves, the other
symptoms gradually subside, and eventually health is regained. It is in
these cases that a strong tendency to disorganization of a destructive
character exists; hence it is we see so many recover imperfectly, with
marked structural changes permanently remaining.
_Subacute._--Subacute laminitis is most often seen as a termination of
the acute form, although it may exist independent of or precede an acute
attack. It is characterized by the mildness of its symptoms, slow
course, and moderate tissue changes. It may be present a long time
before any pathological lesions result other than those found in the
acute form, and when these changes do take place they should be viewed
rather as complications.
_Chronic._--Chronic laminitis is a term used by many to designate any of
the sequelae of the acute and subacute forms of this disease. Pure,
chronic inflammation of the laminae is not very commonly met with, but is
most frequent in horses that have long done fast track work. They have
"fever in the feet" at all times and are continually sore, both
conditions being aggravated by work. Like chronic inflammation of other
parts, there is a strong tendency to the development of new connective
tissue which, by its pressure upon the blood vessels, interferes with
nutrition. Wasting of the coffin bone and inflammation of its covering
with caries is not unusual. The continued fever and impaired function of
secretion result in the production of a horn deficient in elasticity,
somewhat spongy in character, and inclined to crumble. In some cases of
"soreness" in horses used to hard or fast work there is evident weakness
of the coats of the vessels, brought on by repeated functional
exhaustion. Here slight work brings on congestion, which results in
serous effusion and temporary symptoms similar to those of chronic
laminitis.
_Complications._--Complications concurrent with or supervening upon
laminitis are frequent and varied, and are often dependent upon causes
not fully understood.
_Excessive purgation_ is one of the simplest of these, and not usually
attended with dangerous consequences. It rarely occurs unless induced by
a purgative, and the excessive action of the medicine is probably to be
explained upon the theory that the mucous membrane sympathizes with the
diseased laminae, is irritable, and readily becomes overexcited. The
discharges are thin and watery, sometimes offensively odorous, and
occasionally persist in spite of treatment. It may prove disastrous to
the welfare of the patient by the rapid exhaustion which it causes,
preventing resolution of the laminitis, and may even cause death.
_Septicemia and pyemia._--Septicemia and pyemia are unusual
complications and are seen only in the most severe cases in which bed
sores are present or suppuration of the laminae results. They die, as a
rule, within three days after showing signs of the complication.
_Pneumonia._--the so-called metastatic--needs no special consideration,
for in its lesions and symptoms it does not differ from ordinary
pneumonia, although it may be overlooked entirely by the practitioner.
Examinations of the chest should be made every day, so as to detect the
disease at its onset and render proper aid.
_Sidebones._--A rapid development of sidebones is one of the
complications, or, perhaps better, a sequel of laminitis not often met
with in practice. Here the inflammatory process extends to the lateral
cartilages, with a strong tendency to calcification. The deposition of
the lime salts is sometimes most rapid, so that the "bones" are
developed in a few weeks; in other instances they are deposited slowly
and their growth is not noted until long after the subsidence of the
laminitis, so that the exciting cause is not suspected. This change in
the cartilages may commence as early as the first of the laminitis; and
although the trouble in the laminae is removed in the course of a
fortnight the symptoms do not entirely subside, the animal retains the
shuffling gait, the sidebones continue to grow, and the patient usually
remains quite lame. This alteration of the cartilages generally prevents
the patient from recovering his natural gait, and the practitioner
receives unjust censure for a condition of affairs he could neither
foresee nor prevent.
The laminitic process occasionally extends to the covering of the
coronet bone, or at least concurrent with and subsequent to laminitis
the development of "low ringbone" is seen, and it is apparently
dependent upon the disease of the laminae for its exciting cause. The
impairment of function and consequent symptoms are much less marked here
than in sidebones. The coronet remains hot and sensitive and somewhat
thickened after the laminitis subsides, and a little lameness is
present. This lameness persists, and the deposits of new bone may
readily be detected.