Susceptibility in different genera. Reasons for partial immunity of
the quadruped, special and general causes in quadrupeds, violent,
forced work, fatty degeneration, swallowing of pointed metallic
bodies, difficult diagnosis in the animal. Position of the heart in
the horse, ox, sheep, pig, carnivora, birds. Structure of the heart as
a pump. Results of imperfect structure or action. Heart walls. Table
of size of the heart. Capacity. Weight. Pulse in each healthy genus,
according to age, size, environment, temperament, proximity to
parturition. Morbid conditions of the pulse, frequent, slow, quick,
tardy, full, strong, weak, feeble, indistinct, small, hard, wiry,
thready, oppressed, leaping and receding, intermittent, unequal,
irregular, anæmic, venous. Percussion. Palpitation. Auscultation.
Healthy sounds. Morbid sounds, in unusual place, force, intensity,
rythm, repetition of 1st sound, of 2nd sound. Murmurs, synchronance
with given stages of heart movement, their significance, pericardial
murmur. General symptoms of heart disease, cold extremities, passive
congestions, dropsies of limbs, etc., shortness of breath, venous
pulse, vertigo, dulness, sluggishness, corpulence.
The lower animals are perhaps less subject to heart disease than
mankind, but the comparative immunity generally assumed for them is far
from being a real one. The horizontal position of the quadruped largely
obviates that special tax upon the heart demanded by the erect position
of man, and especially by the elevated place given to his more ample and
vascular brain. Animals too are comparatively free from those mental and
moral influences which so largely affect the regularity of the
circulation in the human subject. But on the other hand many physical
causes of heart disease affect the lower creation equally with their
lord, while some undoubtedly operate with special force on the brute.
All animals are subject to diseases of the heart as of other internal
organs, from exposure; this organ is occasionally involved from its
contiguity with other diseased structures or from interdependence of
function as we have already seen in certain diseases of the lungs
(congestion, broken wind, etc.); the tendency to heart disease
frequently runs in a particular family of animals, especially with the
rheumatic constitution, which is transmitted from parent to offspring as
surely as the color of the skin the turn of the horn or the depth and
spring of the rib. The lower animals are further subject to congenital
malformations and imperfections and to deposits of morbid material
around the heart or in its substance so as to impair its healthy action.
Horses and dogs have special predisposing causes in the violent and
prolonged exertion to which they are habitually exposed. The quiet
sluggish and nonexcitable ox and pig meet with dangers no less real
though of a different kind in the overfeeding which induces fatty
degeneration of the heart as of other muscular tissues. The larger
ruminants are further endangered by their propensity to swallow needles
and other sharp pointed bodies which ultimately reach and penetrate the
heart.
The prevalence of heart disease in animals may be deduced from the fact
that out of 150 horses, oxen and dogs dissected at Montfauçon by Leblanc
in 1840, not less than one twentieth presented cardiac lesions. The
supposition of an immunity of the lower animals has been largely due to
the heavy muscular shoulder of quadrupeds which covers the upper and
anterior regions of the heart shutting them out from physical
exploration. In man the entire heart and connecting blood vessels are so
open to examination that the physician can pronounce with the greatest
accuracy not only concerning the existence of disease, but also its
precise locality and nature. In the quadruped no such facility is open
to us, and veterinarians have too generally refused to face the
difficulty, preferring to ignore heart diseases, or still worse seeking
to cover their ignorance by the assertion that such affections rarely
exist. Now however we not only know that heart diseases are much more
frequent in the lower animals than heretofore believed, but that as a
general rule they are sufficiently manifested and recognizable by their
distinctive symptoms.
=Position and exposure of the heart.= In the horse the heart has only
its apex and a small portion of its left ventricle approached to the
surface of the chest, at a point where it is felt to beat behind the
left elbow. The apex approaches the surface in the interval between the
fifth and sixth ribs and close above the breast bone. The posterior
border of the ventricle follows a nearly vertical line upwards from this
point, while the anterior border has a direction upward and forward
crossing diagonally over the fifth rib. The part of the ventricle
exposed extends about three inches upwards from the apex, and is about
two inches in its transverse diameter. The great mass of the organ is
covered by lung substance.
In the =ox= about the same extent of heart tissue is exposed. In =sheep=
a portion about an inch in height and one and a half inches in breadth
is left uncovered by lung. In the =pig= the heart is exposed only in a
triangular space of about an inch across.
In the =carnivora= the heart lies more directly in the median line of
the chest. It appears as if tilted forward so that its apex is directed
backward and its base forward, while the body of the organ lies directly
over the breast bone. The lungs invest it on both sides preventing any
approximation to the walls of the chest laterally, and it can best be
auscultated by applying the ear over the sternum.
In =birds= the heart is situated in the centre of the chest and
enveloped by lung tissue so that its exploration is about equally
difficult at all points.
The larger blood vessels at their origin from the heart are not open to
examination in the lower animals except to a limited extent in the dog.
=Internal arrangement and structure of the heart.= In all warm blooded
animals the heart is composed of two portions, the internal cavities of
which are perfectly distinct from each other and contain blood in
different conditions; the right portion holding the impure, purple or
venous blood which has just circulated through the body, and the left
portion being filled with the bright crimson or arterial blood, which
has been ærated by circulating through the lungs. Each of these portions
is divided into two distinct cavities, an _upper_ (auricle) which
receives the blood from the veins, and a _lower_ (ventricle) which
receives the blood from the auricle and transmits it into the arteries.
The auricle is separated from the ventricle by a transverse
musculo-membranous partition having a large central orifice furnished
with valves (auriculo-ventricular), the free borders of which are turned
downward so that they allow the blood to flow freely downward from the
auricle but completely close the orifice and prevent any reflex when the
ventricle contracts. The great artery which originates from the base of
each ventricle is likewise furnished with a system of valves (semilunar)
having their free borders turned into the artery, so that they allow
blood to flow freely into that vessel during the contraction of the
ventricle, but prevent any reflux into the heart when the ventricle
again dilates. The apparatus may be likened to a force pump with two
systems of valves, one to prevent the return of any water from the pump
into the fountain; the other to hinder any reflux from the delivery pipe
into the pump. Any interference with either of these valves entails a
very serious and usually a fatal disorder of function.
These _orifices_ differ considerably in size. Those between the auricles
and ventricles are considerably larger than those at the commencements
of the great arteries. Those on the right side of the heart too are
greater than those on the left. They vary with the form of the heart.
Thus in dilatation of an auricle and ventricle on one side of the heart,
the auriculo-ventricular opening becomes equally widened and the valves
remaining disproportionately small the blood is allowed to rush back
into the auricle during ventricular contraction. The left
auriculo-ventricular opening has been known to become contracted in some
very flat and shallow chests; the blood failing to circulate freely
through the lungs and to reach the left side of the heart in a full
supply this orifice accommodates its size to the amount, and may become
so narrowed that it forms a serious obstacle to the blood flow and a
series of morbid changes result following the backward course of the
circulation. The auricle first becomes overdistended and its muscular
walls increase in thickness and consistency; the lungs tend next to
suffer from a passive congestion, and lastly the right side of the heart
becomes engorged and enlarged.
Any obstruction in the aorta which conveys the blood from the left side
of the heart equally leads to dilatation of its internal cavity and
abnormal thickness of its walls.
The imperfection of the valves is one of the most serious results of
such changes in heart structure. The sounds by which such imperfection
may be recognized will be presently noticed, meanwhile the mode of
testing this in the heart of the dead animal will be referred to. If due
to structural changes in the valves themselves, the new deposits, the
cicatrices, the lacerations, etc., will be visible to the eye. Though no
such disease-changes are seen the valves may still manifest imperfection
by failing to fulfill their normal function when put to the test. Water
is poured into one or other of the great arteries which arise from the
ventricles, the vessel being held vertically, and if it fails to descend
into the heart the valvular action is perfect. The auriculo-ventricular
valves may be equally tested by filling the ventricle and observing
whether there is a reflux into the auricle.
The =thickness of the walls of the heart= varies in disease. The
auricular walls are invariably thin and flaccid except as above noted
with diminution of the auriculo-ventricular orifice. The walls of the
right and left ventricles differ in thickness in accordance with the
distance to which they have respectively to propel the blood and the
propulsive effort demanded. Thus the walls of the _right ventricle_
which is only called upon to propel the blood through the lungs are only
about ½ an inch in thickness and are thinnest at their lower part. Those
of the _left ventricle_ which have to send the blood to the most distant
parts of the body are from 1 to 1½ inches except at the lower part where
they form the apex of the heart, and are reduced to a tenuity resembling
the walls of the auricles. They are thickest at the median part, and
diminish slightly in an upward or downward direction. The bulk of these
walls is excessively muscular, the fibres arranged as an elaborate
double spiral and connected with a layer of white fibrous tissue placed
in the interval between the auricles and ventricles and surrounding the
auriculo-ventricular openings and the orifices by which the great
arteries take their origin. It is at this point, where the muscular
fibres of the ventricles are connected with the white fibrous rings,
where rupture of the heart usually takes place.
The following measurements may be held to refer to medium sized animals
of the different kinds mentioned.
─────────┬──────────────┬───────────────────────────────┬──────────────
│ Longitudinal │ │
│ Diameter. │Transverse Diameter at the Base│Circumference.
│ Inches. │ of the Ventricles. │ Inches.
─────────┼──────────────┼────────────────┬──────────────┼──────────────
│ │Antero-Posterior│ Transverse │
│ │ Inches. │ Inches. │
─────────┼──────────────┼────────────────┼──────────────┼──────────────
Horse │ 10 │ 7½│ 5⅓│ 19½
Ox │ 9⅘│ 6⅘│ 4½│ 17½
Sheep │ 4 │ 3 │ 2 │ 7⅓
Pig │ 4½│ 3⅗│ 2⅓│ 9⅘
Dog │ 3⅘│ 3⅗│ 2 │ 8½
─────────┴──────────────┴────────────────┴──────────────┴──────────────
The =internal capacity of the ventricles= is so modified by the amount
of _post mortem_ contraction that it differs widely from the actual
capacity during life. The left ventricle of the larger domestic
quadrupeds usually admits from 3½ oz. to over 5 oz., while the right
ventricle whose walls are so much thinner and more lax will contain
double that amount. In the smaller animals about a tenth of these
quantities will be admitted.
=The weight of the heart= too can only be stated as an average or for
medium sized animals. In the _horse_ it may be from 4½ lbs. to 9 lbs.;
in the ox from 3 lbs. 5 oz. to 4½ lbs.; in the _sheep_ from 5½ oz. to 7
oz.; in the _pig_ from 9½ oz. to 14 oz.; and in the _dog_ from 5 oz. to
7 oz. This statement must be understood to apply to dogs approximating
in size to the shepherd’s.
Taking into account the size of the particular animal any considerable
deviation from these measurements and weights may be accepted as
abnormal. The ratio to the body weight is about:—horse and dog 1:100,
ox, sheep and pig 1:220. This necessarily varies with condition—fat or
lean.
The =pulse= offers valuable indications in disease of the heart.
The _number_ of the pulse in healthy full-grown animals may be set down
as follows per minute:—horse, 36 to 46; ox, 38 to 42 (with loaded paunch
or in a hot stable up to 70); sheep, goat and pig 70 to 80; dog 80 to
100; cat 120 to 140; goose 110; pigeon 136; chicken 140. In old age the
pulse is less frequent. This diminution may extend to 5 beats per minute
in the larger quadrupeds and to 20 or even 30 in the smaller. Youth and
small size again are associated with a greater rapidity of the pulse.
The pulse of the foal, at birth, is about three times that of the horse;
in the colt of six months it is double; at a year old about one and a
half times; and at two years old one and a quarter.
The smaller the animal, _caeteris paribus_, the more rapid is the pulse.
Hot buildings, exertion, fear or any other exciting cause likewise
accelerates it. It is more frequent with the nervous temperament, as for
example in the English race horse, or the greyhound, than in the dull
lymphatic cart horse or mastiff. In advanced pregnancy it is increased
in number. In the cow and mare it undergoes a monthly increase of four
or five beats per minute after the sixth month. (Delafond)
Independently of these conditions a rapid pulse indicates febrile
excitement attendant on active inflammatory or other disease, or a state
of weakness and debility. In this last condition the heart beats more
frequently to secure a more rapid circulation in the capillary blood
vessels, and thus make up to the craving tissues by frequency of
contact, what is wanting in the quantity and quality of the nutritive
fluid. This point cannot be too much insisted upon, as the fatal
doctrine that a rapid pulse indicates force of the circulation is very
misleading as to treatment.
The =force and character of the pulse= differ in the various species. In
the =horse= it is full, moderately tense and elastic. In the =ass= and
=mule= it is smaller and harder, with an inequality of force in
successive beats, and sometimes even a beat is suppressed or
imperceptible. In the =ox= the pulse is full, soft and regular,
appearing to roll forward beneath the fingers. In the =sheep= and =goat=
the pulse is small but with a peculiar quick or sharp beat. The =pig’s=
pulse is said to be firm and hard. That of the =dog= and =cat= is firm
and hard coming with a sharp impulse against the finger. In the dog,
however, successive beats are not always of the same force and an
intermission or complete absence of a beat is by no means an indication
of disease of the heart or other serious malady. It often attends the
slightest excitement in a perfectly healthy animal.
In disease the _pulsations_ may become:—=frequent= or increased in
number; =slow= or decreased in number; =quick= or striking with a sharp
impulse against the finger; =tardy= or without sharpness of stroke and
as if they rolled slowly past under the finger; =full= and =strong= when
the impulse is forcible and not easily compressed by the finger; =weak=,
=feeble= or =indistinct= in the opposite conditions; =small= when though
perfectly distinct and forcible they are wanting in fulness; =hard=,
when forcible and jarring (this is sometimes called =wiry= or, if
smaller, =thready=); =soft= when though the artery may be full the beat
is devoid of hardness and easily compressible so as to be unfelt;
=oppressed= when with a full rounded artery, the impulse is jerking
though not hard and as if the distended vessels opposed the transmission
of the impulse; =jerking and receding=—=leaping=, when with empty and
flaccid arteries the pulse seems to leap forward with each beat of the
heart—(this pulsation may be visible to the eye in the carotids);
=intermittent= when after a number of beats at regular intervals there
is a complete pause extending over that period of time which would have
been occupied by a full beat; =unequal= when some beats are strong and
others weak; =irregular= when without any distinct intermission for a
period equal to that of a single beat, the intervals between successive
beats are of varying length. The pulse further has a peculiar =thrill=
or =tremor= in states of great debility with deficiency of blood and
imperfect filling of the vessels.
Of these the =leaping=, the =intermittent=, the =unequal= and the
=irregular= pulses are of special importance in their bearing on heart
diseases.
The =jerking and receding= pulse is felt in cases of imperfection of the
semilunar valves at the commencement of the great aorta, and which
allows blood propelled into the arteries by the contraction of the
ventricle to flow back into the ventricle during its state of
relaxation. This pulse is met with in other conditions as in aneurism of
the aorta, but if from heart disease it is distinguished by the presence
of a _blowing murmur_ with the second sound of the heart.
The =intermittent= pulse indicates functional derangement of the heart
but it does not as is generally believed betoken structural disease. It
is frequently observed in healthy asses and mules, and in dogs however
slightly excited whether by fear or joy, or by the mere fact of their
being handled, it is so common as to be almost the rule rather than the
exception. It may be seen in a healthy horse as the result of
excitement. During the early stages of convalescence from inflammatory
affections of the lungs in the horse the pulse is often intermittent.
The pulsations are at the same time unequal. There is a regular cycle of
beats gradually decreasing in force and extending over a complete
respiratory act. The cycle commences with the strongest beat during or
immediately after the act of expiration, and the succeeding four or five
beats are less and less forcible until the chest is fully expanded when
there is a quiescent interval corresponding to the period of one beat.
In many such cases there is no other indication of heart disease and the
phenomenon appears due to the interference with the circulation by the
hepatized lung, to the impaired nervous energy of the heart and to its
compression between the distended lungs. A pulse simply _intermittent_
and not associated with any further sign of heart disease does not then
possess the significance generally attributed to it, but a careful
examination of the heart should invariably be made when this functional
disorder is observed. It exists or may be brought about by slight
excitement in the great majority of heart diseases.
In case of intermittent pulse it is useful to ascertain whether there is
also an intermission of the heart’s beat, since in softening of the
heart, that organ may beat without being able to transmit the impulse
along the artery.
A pulse at once =unequal and irregular= is a much more serious
indication than a merely intermittent pulse. It is observed especially
in fatty degeneration of the muscular substance, and with imperfection
of the valves on the left side of the organ, though it may be present in
other cardiac diseases independent of the existence of those lesions.
In _hypertrophy of the left ventricle_, the pulse is full and strong and
the impulse appears prolonged, because of the greater length of time
taken up by the ventricle in the act of contraction. When _dilatation_
coexists with _hypertrophy_ the impulse is still full and strong, more
blood being transmitted through the vessel; but when _dilatation_ is
combined with _attenuation_ of the ventricular walls the impulse is soft
and weak by reason of the feebleness of the contractions.
The pulse at the radial artery should be about synchronous with the beat
of the heart. If retarded it may be held to indicate the existence on
the anterior aorta or its primary divisions of an aneurism with elastic
walls or more probably an imperfection of the aortic valves, which
allows a regurgitation of the blood into the heart.
=Venous pulse.= A venous pulse seen in the lower end of the jugular
veins is common in the domestic animals. In the ox it is quite
compatible with health and is only to be judged by its amplitude and
force. In other animals it often coexists with congestion of the lungs
which impedes the circulation through the right side of the heart and
leads to engorgement of the venous system. In the absence of this
condition it frequently indicates an imperfection of the
auriculo-ventricular valves in the right heart and a reflux of blood
from the contracting ventricle which checks the descending current in
the veins.
=Percussion.= In the =horse= a dull, dead sound is emitted when
percussion is made over the left side for about four inches above the
breast bone and in the space corresponding to the lower ends and the
cartilages of prolongation of the fourth, fifth and sixth ribs. In the
ox this dulness is less marked on the level of the sixth rib. The same
results can be obtained on the right side by imparting heavier blows to
the chest walls so as to derive the sound from the deeper parts.
The area of dulness is _increased_ in cases of _hypertrophy_ or in
_dilatation_ of the heart when the enlarged organ presses aside the lung
tissue and exposes a greater amount of its substance to the chest walls.
The same result takes place in hydropericardium.
The area of dullness is _diminished_ in cases of ruptured air cells (as
in “heaves”) when the inflated and expanded lung tissue envelopes the
heart more completely and gives out its own clear resonance where the
dull sound of the heart is usually obtained.
=Application of the hand.= =Palpation.= In conditions of health and in
quietude the hand applied on the side of the chest, close behind the
left elbow only just perceives the beat of the heart with each
contraction. If the animal is excited whether from fear, joy or physical
suffering the heart’s impulse becomes more powerful and by this alone
the state of its function may be very satisfactorily ascertained. The
impulse is strong in all active fevers and extensive inflammations of
important organs, but it is especially marked in diseases of the heart
and lungs. Irregularity in the force of successive beats is seen in
various heart diseases and debilitated conditions are recognized in the
same way.
Any want of harmony between the heart’s action and the pulse may be
observed by laying the right hand over the region of the heart and
applying the fingers of the left on the radial artery. In debility and
especially if from a deficiency of blood the violent or tumultuous
action of the heart contrasts strangely with the weak jerking and
compressible pulse. The same symptoms are noticed when the valves of the
heart close their orifices imperfectly. In convalescence from lung
diseases and in certain diseases of the heart a beat may be felt by the
right hand for which no corresponding pulsation is felt in the radial
artery by the left.
When the heart is hypertrophied the impulse is stronger and is
associated with a full, strong, and rolling pulse. When it is atrophied
the impulse on the chest and pulse beat are equally weak. When water
exists in the pericardium the heart strikes the ribs with less force.
=Sounds of the Heart.= Synchronous with each beat of the heart two
distinct sounds are heard, separated by a short interval, inappreciable
to most ears, and followed by a period of silence. These sounds are
distinct alike in character and duration. The _first sound_ is dull and
prolonged; the _second_ is short and quick. Some idea of these sounds
may be formed by the pronunciation of the two syllables, _lub_—_tip_,
but an acquaintance with the sounds themselves is essential to a correct
conception of them. The period of time occupied by the first sound is
double that taken up by the second and in man and the smaller quadrupeds
the subsequent period of silence is of equal duration with the second
sound. Dividing the time belonging to one revolution of the heart into
four equal periods the first two are taken up by the first sound, the
third by the second sound and the fourth by the interval of silence. In
the horse the silence is more prolonged, and occupies the entire latter
half of the period of a revolution. The relations stand thus:—the first
sound extends over two-sixths of the time, the second sound over
one-sixth, and the silence over three-sixths.
The _first sound_, synchronous with the beat of the heart against the
ribs corresponds also in point of time with the contraction of the
ventricles, the closure and tension of the auriculo-ventricular valves
and the rush of the blood into the great arteries. The second sound
corresponds to the reflux of blood in the arteries and the closure of
the valves between them and the heart. The period of silence represents
the period of rest during which the heart is being filled from the
veins.
In the horse, at rest, the first is the only sound that can be
distinctly heard in many cases, but during the excitement of exercise,
or in febrile conditions the second is sufficiently apparent and any
deviation from the natural character is easily noted.
These sounds are most distinct over the lower end of the fifth and sixth
ribs on the left side, but they may be heard distinctly behind the
middle of the shoulder on either side when the corresponding limb is
advanced. In birds they may be heard beneath the wings but above all and
most clearly over the breastbone.
In =disease= these =sounds= may be heard in unusual situations, they may
be altered in force duration or rythm, or they may be associated with
other sounds or superseded by them.
The sounds may be heard in new situations, in displacements of the heart
from tumors or effusions in the chest, structural changes in the lungs,
pleuræ, or pericardium, aneurism of the aorta, etc., etc.
The heart sounds are clearly heard over any part of the chest when the
lung tissue intervening between that part of the surface and the heart
is solid (hepatized). They are heard distinctly behind the median part
of the right shoulder, when liquid effusion into the left pleural sac
has displaced the heart to the right; and when the right cavities of the
heart are extensively dilated as exists so commonly in the advanced
stages of “_heaves_.”
The =extent= over which the sounds may be heard is _increased_ when the
lung surrounding the heart is solidified (hepatisation, splenisation,
etc.), or when liquid effusion exists in the chest. A liquid but more
especially a solid is a better conductor of sound than the spongy lung.
Enlargement (hypertrophy) of the heart equally increases the area of
sound. The _area_ of sound is lessened by atrophy of the heart, and by
an emphysematous condition of the lungs by which the heart is more
extensively covered and further separated from the walls of the chest.
The =force= or =intensity= of the heart sounds is increased in high
fever, in acute inflammation, in increase of the muscular walls of the
heart with enlargement of the internal cavities, in functional
disturbance from fear or other exciting cause, and in palpitation. Often
in a weak and bloodless patient the heart sounds can be clearly heard at
several yards distance from the animal. The _intensity_ of the sounds is
diminished in debility when not associated with palpitation, in atrophy
of the muscular substance of the heart, in hypertrophy of the muscular
tissue of the heart with diminution of its internal cavities, in _broken
wind_ when the emphysematous lung more completely envelopes the heart,
and in cases of extensive liquid effusion into the pericardium which
prevents the apex of the heart from striking against the side of the
chest.
The regular =rythm=, normally manifested by the two sounds and the
silence, may be modified in the unequal irregular or intermittent
contractions of the heart. Küssmaul’s paradoxical pulse is one in which
the pulse is more frequent but less full during inspiration than
expiration. Seen in weak heart, during recovery from chest diseases, in
chronic pericarditis, and when fibrous bands encircle the root of the
aorta. Bigeminal and trigeminal when two or three beats follow each
other rapidly, and are separated from the preceding and succeeding beats
by longer intervals. This occurs in disease of the mitral valve, and in
other weak states of the heart. Fœtal heart rythm in which the pause is
shortened and the two sounds of the heart are almost identical, is seen
in the later stages of fevers, and in extreme dilation. A curious
aberration of rythm is the _repetition_ of either the first or second
sound. If of the first sound (anapestic bruit) each beat will be
accompanied by three sounds the first two of which resemble the first
sound of health. If the second sound is repeated (dactylic bruit, bruit
de galop) the first sound only will be prolonged and the last two sharp
and quick. The repetition of the last sound is probably due to impaired
nervous supply which allows the completion of the contraction of the
ventricle and the closure of the arterial (semilunar) valves sooner on
one side than the other. If due to diminution of the arterial orifice
which retarded the emptying of one of the ventricles, the first sound
would probably be accompanied by a blowing murmur. If the
auriculo-ventricular valves on one side were imperfect, allowing a
reflux into the auricle and a more rapid emptying of the ventricle a
blowing murmur would equally accompany the first sound. In either of
these two last mentioned cases the murmur would mask or hide the first
of two doubled sounds.
The repetition of the 1st sound is often due to dilatation of one
ventricle, which in consequence is longer in reaching the same sensation
of plenitude, and in receiving the stimulus to contraction.
=Morbid Sounds.= =Murmurs.= The distinct and superadded sounds heard in
disease are usually designated murmurs. They originate in the interior
of the heart (endocardial) or externally to the heart (pericardial). The
=endocardial= sounds mostly arise from some abnormal conditions of the
valves or orifices and consist in a blowing or rushing noise which
usually accompanies or displaces one of the heart sounds, though it may
precede or succeed these. The following table modified from that of
Bartle and Roger presents at a glance the relations of these different
sounds and their significance.
Blowing or Hissing Murmurs.
Blowing murmur before │Narrowing of the auriculo-ventricular orifice.
the first sound. │ Vegetations or coagula on the valves.
│Strongest toward the │
Blowing murmur with the│ base of the heart. │Narrowing of the aortic
first sound. │ Propagated along the │ opening.
│ great arteries. │
│Strongest toward the │Narrowing of the
│ apex of the heart. │ pulmonary artery or
│ Not propagated in the│ insufficiency of the
│ great arteries. │ auriculo-ventricular
│ │ valves.
│Double rushing sound │Insufficiency of the
Blowing murmur with the│ heard over the great │ arterial (semilunar)
second sound. │ arteries at each beat│ valves.
│ of the heart. │
│Double rushing sound in│
Blowing murmur after │ the arteries with │Aneurism (dilatation of
the second sound. │ each beat of the │ the great aorta.)
│ heart. │
From the table it will be seen that each orifice in the heart may become
the seat of two perfectly distinct and independent murmurs; one due to
constriction of the orifice in which case the sound is produced with the
onward progress of the blood wave; and one due to dilatation of the
orifice or insufficient closure of it by the valves, when the sound is
due to a recoil or regurgitation of the blood. There is a further sound
due to mere roughness of the valves in cases of disease when the sound
will be with the normal current of blood, though a second or regurgitant
hiss is often heard from the valves being at the same time insufficient
to close the orifice. Another blowing murmur is usually heard over the
heart and coincident with its first sound in the bloodless state
(anæmia). This is not necessarily connected with any diseased condition
of the heart itself.
The nature of these murmurs differs in special instances. They may
resemble the soft whisper of the words _who_ or _awe_, of the double
letter _ss_, or the single letter _r_, according as they are soft or
hard and purring.
The =pericardial murmur=, caused by the rubbing of the dry roughened
surface of the serous membrane covering the heart on the correspondingly
dry rough surface of the same membrane, reflected on the investing sac,
resembles that caused by passing the palm of the one hand over the other
which lies on the ear. It is distinguished from the friction sound of
pleurisy by its coinciding with the movements of the heart and not with
those of respiration. It is usually heard alike during the sounds of the
heart and during the period of silence or in other words during the
movements of contraction and dilatation in that organ.
=General Symptoms of Heart disease.= In the acute inflammatory
affections there are the signs of general constitutional disturbance
attending similar affections in other organs. The decision as to the
true nature of the disease must be arrived at from the special character
of the pulse, heart sounds, etc. as already noticed.
In the chronic forms of the disease however a particular class of
symptoms usually point towards the organ affected. In cattle, sheep and
pigs raised only for slaughter, and as far as possible protected against
active exertion, serious heart diseases may exist for a length of time
without making themselves manifest by any prominent symptoms. Thus in
cows, pins and other sharp pointed bodies swallowed with the food
frequently make their way to the heart and lodge for a length of time in
its vicinity without material derangement and when at last the animal
dies a sudden death they are found transfixing the walls of that organ.
In the horse or other animal subjected to exertion the symptoms are
usually very patent.
When the heart is enlarged the pulse strong and the circulation full and
free, apoplexies or hemorrhages especially on the brain or other soft
organs where the resistance is least, are liable to occur. When on the
other hand the circulation is weak from atrophy or fatty degeneration of
the heart, or from insufficiency of the valves there is a tendency to
coldness of the extremities, and to passive congestions with their
consequences:—serous effusions, dropsies, and difficult breathing. The
imperfect supply of blood to the muscles of the extremities sometimes
brings about an unsteadiness of gait in the hind limbs when the animal
is trotted for a short distance and sometimes cramps supervene.
Continued coldness of the limbs, and a filling or thickening first of
the hind limbs then of the fore and lastly of the chest and belly and of
the skin beneath their dependent parts are useful indications.
Shortness of breath and inability to proceed when trotted or galloped on
hard ground or when walked up hill, the animal being in fair condition,
without fever or cough, but subject to cold extremities and a venous
pulse in the jugulars, almost certainly indicates insufficiency of the
auriculo-ventricular valves on the right side of the heart.
Vertigo megrims or giddiness may be caused by heart disease. The horse
without having sustained any pressure on the veins of the neck by the
collar, and having had no previous symptom of brain disease suddenly
reels in harness and perhaps falls. There are the cold and engorged
limbs or a tendency to their engorgement as in the former case. The
attacks recur, when the horse is put to the same exertion, and he proves
utterly worthless. In such cases a careful examination of the pulse and
heart sounds will complete the chain of evidence.
An almost constant feature of chronic heart disease is a condition of
dulness, sluggishness, and in many cases, curiously enough, a tendency
to lay on fat, so that although the patient is unfit to work, he appears
to enjoy excellent general health to which a period is only put by
sudden death.
Affections of the heart are primarily divisible into _functional_ and
_structural_ disorders.