On the physiology of asphyxia and on the anaesthetic action of pure nitrogen / by George Johnson.

  • Johnson, George, 1818-1896.
Date:
1891
Catalogue details

Licence: Public Domain Mark

Credit: On the physiology of asphyxia and on the anaesthetic action of pure nitrogen / by George Johnson. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    the vaso motor nerves and centre, the muscular arterioles1 are excited to contract, and by this action of the vaso- constrictors the blood pressure in the arterial trunks is increased, while the left cavities of the heart become dis- tended and dilated, as seen in Fig. 1. The circulation through the systemic arterioles is impeded and lessened, but not entirely arrested ; some black blood passes through the capillaries, and this venous blood, becoming more and more entirely deoxidised, reaches the right side of the heart, and the pulmonary vessels, and coming in contact with the pulmonary arterioles, it excites in them the same.contraction and resistance as had before occurred in the systemic vessels. The resistance offered by the pulmonary vaso constrictors, while on the one hand it tends to empty the left side of the heart and to lessen the blood pressure in the systemic arteries, on the other it causes that great distension of the right cavities and of the systemic veins which is invariably found when the chest is opened immediately after death from asphyxia, and which in such experiments as Dr. Rutherford’s are plainly seen to occur during the lifetime of the animal. (See Fig. 2)] The relative amount of blood on the two sides of the heart is not an exact measure of the degree of pulmonary obstruction which has existed during the last moments of life, for the reason that the impairment of the contractile power of the left heart by anaemia and venous blood appears to vary in different cases; but I may here mention the results of the simple experiment of ligaturing the trachea of a dog which has been twice performed in my presence ; the chest having been opened and the amount of blood in the two sides of the heart measured immediately after the animal had ceased to struggle. i It has been shown in Ludwig’s laboratory that the arteries of an organ which has been withdrawn from all nervous influence contract when blood overloaded with carbonic acid flows through them. See Conheim’s Lectures on General Pathology : New Sydenham Society's Transactions, p. 112