The action of an active principle from apocynum / by H.H. Dale and P.P. Laidlaw.

  • Dale, Henry Hallett, 1875-1968.
Date:
1909
Catalogue details

Licence: Attribution 4.0 International (CC BY 4.0)

Credit: The action of an active principle from apocynum / by H.H. Dale and P.P. Laidlaw. 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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    short time after the ventricle remains firmly contracted. Fig. 3 shows the result of recording by the suspension method at various stages. Fig. 3. Heart of decerebrate frog. Suspension method. Upstroke = systole. Min. vii 1 : 5,000 Cynotoxin injected into dorsal lymph sac. A—Normal. B—3 minutes after injection. C—fi minutes after injection. D—10 minutes after injection. Time in seconds. Tracings of isolated frogs’ hearts, perfused with Ringer’s solution (through the sinus venosus), were also taken; addition of Cynotoxin caused the development of a precisely similar series of phenomena, to those observed in the pithed amphibian. To obtain a measure of the ventricular volume under the influence of the drug, we used Locke’s modification of Williams’ appara- tus*. This gives an accurate record of the output of the ventricle while the heart perfuses itself. We found Dixon’s'5 frog-intestine volume-recorder very useful with this apparatus. Cynotoxin or Apocynamarin in quite weak concentration (1 in 500,000 to 1 in 200,000) produces an increased output, and a very similar sequence of effects to those observed in pithed animals, con- cluding with systolic arrest (Fig. 4). One variation should be mentioned ; the initial decrease of volume frequently gives way to a secondary dilatation, the tonus subsequently recovering, and then increasing till systolic arrest becomes complete. This difference is doubtless due to the fact that, in the perfusion apparatus, the pressure on the interior of the ventricle remains constant, and may secondarily distend the ventricle in spite of its systolic effort. Indeed, with a sufficiently high inflow pressure, a final quiescence in a condition of distension, simulating true diastole, may be obtained. In the pithed frog, on the other hand, the pressure falls with the failing output, and nothing but the efforts of the auricle hinders the passage of the ventricle into complete contraction. In addition to this characteristic digitalis-like action on the frog’s heart Cynotoxin or Apocynamarin has a pronounced effect on the plain muscular tissues of that animal. The action was examined on :— 1. The plain muscle of the arteries ; 2. The plain muscle of the stomach. * This apparatus was shown at a meeting of the physiological society, but a full description has not yet been published. Through the kindness of Dr. Locke we have been able to use it in the incomplete form.