DISEASES OF THE HEART AND ORGANS OF CIRCULATION.
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. Inches. | Transverse Diameter at the Base of the Ventricles. | Circumference. Inches. | ||
|---|---|---|---|---|
| Antero-Posterior Inches. | Transverse 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 the first sound. | Narrowing of the auriculo-ventricular orifice. Vegetations or coagula on the valves. | |
| Blowing murmur with the first sound. | Strongest toward the base of the heart. Propagated along the great arteries. | Narrowing of the aortic opening. |
| Strongest toward the apex of the heart. Not propagated in the great arteries. | Narrowing of the pulmonary artery or insufficiency of the auriculo-ventricular valves. | |
| Blowing murmur with the second sound. | Double rushing sound heard over the great arteries at each beat of the heart. | Insufficiency of the arterial (semilunar) valves. |
| Blowing murmur after the second sound. | Double rushing sound in the arteries with each beat of the heart. | Aneurism (dilatation of the great aorta.) |
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.