A textbook of human physiology / translated from [the] 6th German edition by W. Stirling.

  • Landois, Leonard
Date:
1888
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Licence: Public Domain Mark

Credit: A textbook of human physiology / translated from [the] 6th German edition by W. Stirling. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    137/980 page 85
    {Krcinrd-cr). It is nuite clear, therefore, that the relation of the strength of the stimnlus to the extent of the contraction of the cardiac mnscle, is quite ditlereut from what occurs in a muscle of the skeleton, where within certain limits the amplitude of the contraction bears a relation to the stimulus, while in the heart the contraction is always maximal.'] Human Heart.—V. Ziemssen found that he could not alter the heart-beats of the human heart {Fran Serafiii, § 47, 3), even with strong induction-currents. The ventricular diastole seemed to be less complete, and there were irregularities in its contraction. By opening and closing, or by reversing a strong constant current applied to the heart, the number of beats was increased, and the increase corresponded with the number of electrical stimuli ; thus, when The electrical stimuli were 120, 140, 180, the number of heart-beats was the same, the pulse beforeiuind being SO. The normal pulse-rate of 80 was reduced to 60 and 50 wheji the luimber of shocks was reduced in the same ratio. [In Fran Seralin's case the electrodes were apjdied to the heart, separated from it merely by the pericardium. Ziemssen found that the Faradic current did not modify the heart's action when the thorax was intact, but that the constant current did; if of sufficient strength. Herbst and Dixon Mann obtained negative results with both kinds of electricity in the normal thorax.] {(1) Chemical Stimuli.—Many chemical substances, when applied in a dilute solution to the inner surface of the heart, increase the heart-beats, while if they are concentrated, or allowed to act too long, they diminish the heart-beats, and paralyse it. Bile, and hile salts, diminish the heart-beats (also when they are absorbed into the blood as in jaundice) ; in very dilute solu- tions both increase the heart-beats. A similar result is produced by acetic, tartaric, citric, and phosphoric acids. Chloroform and ether, applied to the inner surface, rapidly diminish the heart-beats, and then paralyse it; but very .small quantities of ether (1 per cent.) accelerate the heart-beat of the frog [Kroncckcr and M'Grcgor-Mobertson), while a solution of 1^ to 2 per cent, passed through the heart arrests it temporarily or completely. Dilute solutions of opium, strychnia, or alcohol applied to the endocardium, increase the heart-beats ; if concen- trated they rapidly arrest its action. Chloral-hydrate paralyses the heart. Action of Gases.—When blood containing different gases was passed through a frog's heart, Klug found that blood containing sulphurous acid rapidly and com])letely killed the heart ; chlorine stimulated the heart at first, and ultimately killed it ; and laughing-gas rapidly killed it also. Blood containing sulphuretted hydrogen paralysed the heart without stimulating it. Carbonic oxide also paralysed it, but if fresh blood was transfused the heart recovered. [Blood containing 0 excites the heart (C'astcU), while the presence of much CO.^ paralyses it, and the presence of CO., is more injurious than the want of 0. Blood or serum completely saturated with CO^ exhausts the heart {Saltet ami Kronecker), but it recovers itself when the COo is removed. H and N have no effect.] Cardiac Poisons are those substances whose action is characterised by special effects upon the movements of the heart. Amongst these are neutral potash salts, which cause the heart to stand still in diastole. An excised frog's heart ceases to beat after one-half to one minute when it is placed in a 2 per cent, solution of potassic chloride.] Even a very dilute solution of yellow prussiate of potash injected into the heart of a frog causes the ventricle to stand still in systole. Antiar (.Java arrow-poison) causes the ventricle to stand still in systole and the auricles in diastole. Some heart-poisons, in small doses, diminish the heart's action, and in large doses not unfrequentl}' accelerate it, e.q., digitalis, morphia, nicotin. Others, when given in small doses, accelerate its action, and in large doses slow it—-veratria, aconitin, camphor. Special Actions of Cardiac Poisons.—The complicated actions of various poisons upon the heart have led observers to suppose that there are various intra-cardiac mechanisms on which these substances may act. Besides the muscular fibres of the heart and its automatic (jnriglia, some toxicologists assume that there are inliibitory ganglia into which the inhibitory fibres of the vagus pass, and accelerator ganglia, which are connected with the accelerating ncrve-fibres of the heart. Both the inhibitor]] and accelerator ganglia arc connected with the automatic ganglia by conducting channels. Muscarin and all other trimcthylammonium bases stimulate permanently the inhibitory ganglia, so that the heart stands still {Schmiedeberg and Koppe). [According to Gaskell, how- ever, when the action of the sinus is arrested by muscarin, there is no deflection of the galvano- meter similar to that produced by the excitation of the vagus. He infers that muscarin docs not cause arrest of the beat by acting as an excitant of inhibitory mechanisms, but as a depressant to motor activity.] As atro]iin and daturin paralyse these ganglia, the standstill of the heart brought about by muscarin may be set aside by atropin. [If a frog's heart be excised and placed in a wMtch-glass, and a few drops of a very dilute solution of muscarin be placed on it with a pipette, it ceases to beat within a few minutes, and will not beat again. If, however, the muscarin be removed, and a solution of atropine applied to the heart, it will resume its con- tractions after a short time.] Physostiginin or Calabar bean excites the energy of the cardiac muscle to such an extent, that stimulation of the vagus no longer causes the heart to stand still, lodine-aldehyd, chloroform, and chloral-hydrate jiaralyse the automatic ganglia. The heart stands still, and it cannot be made to contract again by atropine. The cardiac muscle itself remains excitable after the action of muscarin and iodine-aldchyd, so that if it be stimulated
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