Page:Encyclopædia Britannica, Ninth Edition, v. 11.djvu/587

Rh HEART 553 of each, it is only by taking advantage of certain well-known laws regulating the conduction of sound that we are able to differentiate the sounds produced at each of these open ings respectively, and to assign to each a definite position on the chest-wall, where it is heard at its maximum intensity. Physiology, on the other hand, teaches us that each indi vidual cardiac pulsation, the time of which is marked for us by that impulse against the chest-wall of which we are all more or less conscious, consists of alternate acts of con traction and dilatation affecting the four cavities of the heart. Some of these acts precede this impulse, some accompany it, and others follow it, and the relation of any sound produced within the heart to these physiological acts is termed its rhythm. The functional perfection of the heart is thus easily determined by ascertaining that it is of a normal size, that its impulse is neither too strong nor too weak, and that its sounds are normal when listened to, each in its own position of miximum intensity. When these conditions are present, any abnormal cardiac phenomena, such as palpitation, irregular action, &:., are to be regarded as entirely due to abnormal innervation, and not to any actual disease of the heart. On the other hand functional imperfection is readily detected by the occurrence of any abnormality in the phenomena already referred to, especially if accompanied by a blowing sound instead of the usual valve sound in any of the normal auscultatory areas. And an intelligent appreciation of thase facts, together with a correlation of the physical with the physiological phenomena, that is, a correct determination of the rhythm of the sounds heard, enables us to ascertain with certainty, not only the valve implicated, but also the mode in which the lesion has affected or is likely to affect the heart and through it the circulation. Having found the heart to be functionally imperfect, we have two alternatives presented to us either the valves are incurably deformed from previous disease, or they are merely functionally imperfect from over-disten- tion of the cardiac cavities, a state of matters which may arise from various causes, and which is always susceptible of great relief and very often of perfect cure. The great function of the heart is to keep up such a pressure within the arterial section of the vascular canals as will suffice for the maintenance of the circulation and of all the organic functions of the body dependent upon it. The tendency, however, of all the extrinsic forces connected with the circulation is to equalize the blood pressure throughout the vascular system, and so to bring the circula tion to a stand-still ; and indeed it is in this way that death at last occurs ; whether it happen suddenly or slowly the cause is still the same cessation of the circulation brought about by equalization of the blood pressure throughout the whole of the vascular system, or, as it may be otherwise put, from decline of the arterial (aortic) blood pressure. Valvular lesions of the heart, however produced, tend, as may be readily understood, to neutralize the cardiac function and to lower the arterial blood pressure, either by permitting an unnatural escape of the blood backward (regurgitation) or by obstructing its onward flow (obstruc tion). And this action is further intensified by the inter ference with the cardiac nutrition which necessarily results, first of all directly, from the heart being flushed with blood at a low pressure, and secondly indirectly, from the imperfect performance of all those functions, such as digestion, &c., upon which the formation of healthy blood depends, arising from the same cause. Valvular disease thus gives the heart more work to do, while it takes from it the power of doing it, putting the organ in a vicious circle. In this way curable disease if neglected may readily lapse into incurability, while to incurable disease there can be but one ending, though, apart from such accidents as embolism or asystole from violent emotion or exertion, that is neither so sudden nor so speedy as is commonly supposed, and indeed usually occurs from gradual asthenia, often accompanied by dropsy, and preceded by a life of more or less active exertion, averaging in many cases not less than twenty years from the primary onset of the disease. During this comparatively long period the disease may have been entirely mute ; that is, the valve lesion has progressed so slowly from its trifling commence ment that the residual accumulation in the cavity primarily affected has gone on gnttatim, and has spread itself back wards over the other sections of the circulation in the same gradualmanner, the resulting dilatation being so immediately followed by compensating hypertrophy that the sufferer has never been aware of any derangement of his functions. A time comes at last, however, when, from a failure of nutri tion due to physical causes, the increase in the heart s bulk ceases to be muscular, it becomes fibrous; then indeed the disease is no longer mute, serious rupture of the compensa tion sets in, and all that art can do is to make the inevitable declension as gradual as possible. Up to this period any accidental rupture of the compensation, which readily enough occurs from over-exertion, imperfect nutrition from any cause, or from any feverish attack, is as a. rule perfectly amenable to appropriate treatment, though the restored com pensation is always less stable than it had been previously. Ruptured compensation is often attended by very alarm ing symptoms, such as great general dropsy and extreme irregularity of the heart s action, but the true measure of the patient s danger lies less in these symptoms than in the condition of the cardiac muscle, and in the circumstances which threaten asystole, that is, arrest of the heart s action. If in early times the diagnosis of diseases of the heart was a matter of great difficulty, this seemed of less import ance as their treatment was so hopeless. &quot; A mcsure qu on penetre,&quot; says Senac, &quot;dans les maladies du coeur, la medicine parait plus sterile ; que peut-on espe&quot;rerdes me&quot;di- caments, par exemple, dans les dilatations du coeur 1 &quot; But modern science, which has rendered the heart so accessible from all sides that there is nowadays probably no organ of the body whose diseases can be so readily detected or so accurately discriminated, has not only pointed out the true source of danger in these diseases, but has also put into our hands a remedy by which some are cured who were formerly thought incurable, while many incurables have their downward progress so successfully arrested that they feel themselves to be practically cured. And yet DIGITALIS (q.v.) was all but unknown 100 years ago, while so little was known of its real action ratio medendi that within the last thirty years a living author wrote that the use of digitalis as a diuretic in heart disease was quite &quot; indefensible,&quot; as &quot; the failing heart is absolutely incap able of sustaining the depressing influence of the drug.&quot; Nowadays we know digitalis to be the only drug that can be relied on for increasing the power of the heart s contrac tions, and it also slows them, the result being that the blood pressure is increased throughout the whole arterial system, and that, time being given for the heart itself to be flushed by blood at an increased pressure, its nutrition is improved. The heart not only acts more powerfully under the immediate influence of the drug, but it becomes more able to act, so that by and by the drug may be left off ; though indeed, should the muscular degeneration deter minately threaten a rapid progression, tonic doses of the drug may be safety given daily for many years continuously, in spite of all our forefathers croaking as to the dangers of accumu lation. But however marvellous the effects of tonic doses of digitalis may be, the virtues of the drug in larger doses are even more wonderful in appropriate cases, for by means of large doses the skilled physician has it in his power XI. 70