Theory of the inverse ratio which subsists between the respiration and irritability, in the animal kingdom / [Marshall Hall].

  • Hall, Marshall, 1790-1857
Date:
1832
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Licence: Public Domain Mark

Credit: Theory of the inverse ratio which subsists between the respiration and irritability, in the animal kingdom / [Marshall Hall]. Source: Wellcome Collection.

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    respiration, the left ventricle ceased to beat, the right ventricle retaining its function ; on renewing the respiration, the left ventricle resumed its beat. It appears from this experiment, that from want of a degree of irritability equal to that of the right ventricle, and its own proper stimulus of arterial blood, the left ventricle ceased its contractions. The function of the right ventricle must soon cease in consequence, from want of a supply of blood. These facts prove that arterial blood is the necessary stimulus of the left side of the heart, its irritability being low; but that venous blood is a sufficient stimulus of the right, from its higher irritability: the phenomena plainly flow from the law, that the quantity of respiration and the degree of irritability, observe an inverse ratio to each other, and from the facts on which that law is founded. In this double sense, besides that of distinct cavities, the mammalia have, therefore, two hearts ; and as the highly aerated blood of the left is the peculiar property of birds and the mammalia, so the highly irritable fibre of the right may be compared to that of the heart of reptiles and the fishes. Except for the objection to new terms, the left side of the heart might be termed arterio-contractile, and the right veno-contractile ; the first being stimu- lated by arterial, the second by venous blood. It is quite obvious that the heart will bear a suspended respiration better, the more nearly its irritability approaches to that which may be designated veno-contractile. The power of hearing a suspended respiration thus becomes a measure of the irritability. It is expressed, numerically indeed, by the length of time during which the animal can support a suspended respiration; a con- clusion of the highest degree of importance in the present inquiry. Birds die almost instantly on being submerged in water; the mammalia survive about three minutes, the reptiles and the batrachia a much greater length of time. The unborn foetus, the young animal born with the foramen ovale open, the reptile, the mollusca, having all a state of the heart approaching to the veno- contractile, bear a long-continued suspension of the respiration, compared with the mature animal of the higher classes. But the most remarkable fact deducible from this reasoning is the follow- ing; if such a case existed as that of the left side of the heart being nearly or absolutely veno-contractile, such an animal would bear the indefinite suspen^