Monthly retrospect of the medical sciences : January to December 1849 / edited by George E. Day, Alexander Fleming, W.T. Gairdner.

Date:
MDCCCXLIX [1849]
Catalogue details

Licence: Public Domain Mark

Credit: Monthly retrospect of the medical sciences : January to December 1849 / edited by George E. Day, Alexander Fleming, W.T. Gairdner. Source: Wellcome Collection.

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    respiratory movements, reflux being pre¬ vented during expiration by the valves in the veins at the base of the neck; and in the vena cava inferior, he attributes a val¬ vular action to the displacement of the liver during expiration, which diminishes the calibre of the vein at its passage through the diaphragm. Dr Baumgarten considers the pulsatory movements observed in the healthy state of parts in the great veins, to depend on the sudden interruption of the eurrent of blood during the auricular systole. That the auriculo-ventricular valves are closed by the counter pressure of the ven¬ tricular blood, suddenly developed by the contraction of the auricles. That the cavities of the auricles and ventricles, during the heart’s diastole, are distended by the continuous current from the veins; while at this period the valves are to be found floating in the blood in the form of a funnel. That the object of the auricular systole is to induce such an amount of tension in the contents of the ventricles, and of course in the blood suiTounding the funnel-shaped arrangement of the valves, as to cause their rapid closure; and that in this way only can regurgitation be pre¬ vented. If the heart be removed from the body, and the auricles cut away (it is better, however, to operate with one only), the artery obstructed by ligature, or by filling it with wax, and the cavity of the ventricle filled with a saline solution, the valve is found lying in the position above described. If then a stream of water be directed upon the valve from the height of a foot, so as to imitate the sudden con¬ traction of the auricle, the valve is seen to close with great rapidity. If, however, an attempt be made to imitate the ventri¬ cular systole, by squeezing the ventricle with the hand, a large portion of its eon- tents regurgitates before closure is efiected. That the closure is not due to the opera¬ tion of the musculi papillares, but that it is much facilitated by the small specific gravity of the valves, which enables them to float on the surface of the blood. Dr Hamemik then proceeds to make some remarks, which he considers in part deducible from the preceding. 1. It is possible that there may occur one or more systoles of the ventricles, un- preeeded by any auricular action, fonning what is called the “ rythmus intercurrens ” of the heart’s action. In chronic asthma and pneumonia, the blood, powerfully pro¬ pelled by the expiratory movements, may distend the auricles to such an extent, that they are unable to contract on their contents. In which circumstances, two or more systole.? of the ventricles are re¬ quired before the auricles can unload themselves. 2. The division by the older anatomists of the ventricles into portio auricularis and portio arteriosa, is physiologically and pathologically significant. In the former, there is a current of blood until the closing of the auriculo-ventricular valves, continuous with that of the veins. In the latter, a current is established by the ventricular systole, continuous with that of the arteries. Where there is no motion of fluid, there can be no murmur; consequently simple roughness of the mi¬ tral valve by exudation, or otherwise, will not give rise to a murmur with the first sound unless the valve be also insufficient. 3. The mechanism by which the valves of the arteries are closed, is similar to that of the auriculo-ventricular valves. Im¬ mediately on the contraction of the ven- nicles, the pressure of the blood attained in the large arterial trunks, acting equally in all directions, effects the closure of the semilunar valves. Their complete closure occurs contemporaneously with the end of the ventricular systole. When the ven¬ tricular diastole begins, the arterial re¬ traction commences, and the wave of re¬ flux from the large arteries, falls upon the valves already closed, and thus is produced the clear second sound. There is no re¬ gurgitation, which would necessarily be the case to a certain extent were the valves shut only by the returning wave of blood. 4. The first sound of the heart is occa¬ sioned by the vibration of the tense auri¬ culo-ventricular valves, acted on by the blood propelled against them during the systole of the ventricles, and the vibration of the chordae'tendinese. In like manner, the second sound is produced by the im¬ pulse of the blood on the semi-lunar valves already shut, and not by their closure. 5. A double or even a treble sound is sometimes heard over the ventricles, whieh has been ascribed to various causes, but is probably due to a double vibration of the tense auriculo-ventricular valves—just as a sail struck by the wind may emit several sounds. The same explanation is given when the phenomenon occurs with the second sound. In contraction of the mitral orifice, there is occasionally heard a peculiar sound termed cliquetis metallique, or “ audible heart impulse,” and of which different ex¬ planations have been offered. According to the author’s experience, all true heart sounds are heard by mediate or immediate auscultation only. This sound, however, is heard at a distance from the chest, and is hence presumed by him to depend on