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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    heart were a result of backward pressure from the left, not only would the pulmonary capillaries be engorged, but the pressure in the pulmonary veins would be greater than that in the pulmonary artery, the fact being that the venous pressure is so much less than the arterial, that it can be measured only by a water manometer.] A most complete demonstration of the condition of the heart’s cavities in the different stages of asphyxia was afforded by some experiments performed by Dr. Ruther- ford, now Professor of the Institutes of Medicine at the University of Edinburgh, which I had the privilege of witnessing when he was my colleague at King’s College in the year 1873. The following is a brief description of Dr. Rutherford’s experiments. Into the trachea of a large dog, previously anfB3thetised by chloroform, a tube was tied, and connected with a bellows for the performance of artificial respiration. The voluntary muscles were then paralysed by the injection of a moderate dose of curare, and the animal was kept alive by artificial respiration. The sternum and portions of the ribs were removed, and the pericardium was opened, so as to expose the anterior surface of the heart. One common carotid artery was divided, and a dynamometer tube connected with a mercurial kymograph was introduced into the proximal end. Artificial respira- tion was now suspended, and immediately the colour of the left auricle changed from crimson to purple, the dark venous blood showing through the thin walls of the auricle, while the kymograph indicated a continuous rise of pressure in the systemic arteries, the variations of arterial pressure being registered by a pen on a revolving cylinder. After the in- crease of pressure had continued for about a minute the left cavities of the heart were much distended, the auricle in particular becoming expanded into a tense globular ball with a smooth surface. (See Fig. 1.) In the next period the pressure in the systemic arteries began to fall, and about the same time the right cavities of the heait, which had hitherto remained of the normal size and form,