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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    (, *5 ) effect of contraction of the systemic arterioles is a fall of pressure in the systemic veins, no such fall of pressure has been observed to occur in the pulmonary veins when the increased blood pressure in the pulmonary artery and anaemia of the capillaries indicate that the vaso-constrictors of the lungs are impeding the onward flow of the blood. As there is a direct relation between the anaemia of the minute vessels of the lungs and the collapse of those organs when the chest is opened, and as the anaemia is the result of contraction of the pulmonary arterioles, it is obvious that the greater the resistance resulting from this arterial con- traction the greater will be the pressure to which the pul- monary veins will be subjected by the elastic tissue of the collapsed lungs.] With reference to the innervation of the pulmonary vessels, Drs. Bradford and Dean have proved not only the existence of pulmonary vaso-motor nerves, but also that they leave the spinal cord higher up than the systemic vaso-motor nerves.1 True, these authors remark that “it is probable that the pulmonary vaso-motor mechanism is but poorly developed compared with that regulating the systemic arteries.” It would, however, be a strange and incredible physiological anomaly if the vessels of an organ through which the entire blood of the body has constantly to pass had not the same regulating and resisting power, compared with the force of the right ventricle, as that possessed by the systemic arterioles. Mr. Martin has found, by introducing a manometer into a branch of the pulmonary artery of a moderate-sized cat, while the remaining branches are suddenly obliterated, that the blood pressure in the pulmonary artery rose from 17 mm. of mercury to 36 mm. But neither this nor any other experiment which has been hitherto devised can accurately measure the resisting power of the pulmonary arterioles or the actual force of the right ventricle, for the obvious reason that the arrest or great diminution of the pul- 1 Proc. Roy. Soc., vol. xliv., No. 277.