Observations on some points in dextral valvular disease of the heart / by Alexander Morison.

  • Morison, Alexander (Alexander Blackhall), 1850-1927.
Date:
[1880]
Catalogue details

Licence: Public Domain Mark

Credit: Observations on some points in dextral valvular disease of the heart / by Alexander Morison. Source: Wellcome Collection.

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    position of the lungs in the two animals. In the sheep these organs may be considered to be superimposed upon the heart, and to lap it round from above downwards, whereas the lungs in man may he said to be mainly behind the heart, and to surround it from behind forwards. The result of such an arrangement is, that blood propelled by the right ventricle into the pulmonary circula¬ tion of the sheep must rise, to some extent, in defiance of gravita¬ tion, whereas the pulmonary vessels of man are so placed that a considerable portion of the pulmonary circulation lies below the level of the principal branches of the pulmonary artery, and the blood is assisted instead of impeded in its progress by the law of gravity. Hence, I believe, the proportionately stronger right ventricle of the sheep. But, as I shall presently show, the greater the muscular development of the ventricles, the greater the resi¬ liency of these chambers after systole, and the more powerful their suction force towards the ventricle, provided the capacity of the latter be not at the same time diminished. The influence, there¬ fore, exerted by the more powerful right ventricle of the sheep in suction is greater than that exerted by the thinner right ventricle of man, and any advantage which might be obtained by the latter in this respect, in consequence of its greater capacity, is nullified by its having to deal with a larger quantity of blood than the same chamber in the sheep. The lungs, then, are so placed in this animal as to necessitate by their jDosition a pow^erful ventricle for the due propulsion of blood through the pulmonary circuit, and by so doing at the same time contribute an absorptive force of greater power than that in man, to assist in conducting a circulation naturally more difficult than in the latter. What I have stated with regard to the sheep probably applies more or less to the majority of quadrupeds, but, not having per- j sonally investigated the matter in other animals, I am unable to I state this as a positive fact. We know, however, that the sper- - i matic arteries of the bull are like those of the ram, long and I tortuous, and that in many of the lower animals retia mirabilia i exist. We may, therefore, conclude that in such animals there are I also those conditions of the circulation and circulatory apparatus which we have seen require the presence of these bulwarks against excessive impulse in the sheep. The information derived from this comparison of the vascular system of a biped and a quadruped, appears to me to warrant the conclusion, that the most perfect compensation in cases where the venous circulation is impeded from any cause, whether valvular 1 disease of the right heart or obstruction in the pulmonary circula¬ tion arising in the manner already described from such valvular i disease, or from an independent chronic lung affection, would be I' by an accessory development of both the right and left chambers ; of the heart, the former supplying by suction a vis-a-fronte to ; supplement the great suction force of respiration, and the latter an
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