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XLII.—On a Lower Limit to the Power exerted in the Function of Parturition

Published online by Cambridge University Press:  17 January 2013

J. Matthews Duncan
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Extract

The dynamics of natural labour have been the field of very little successful study or investigation. The object of the present paper is to make a contribution to this subject. I purpose to show what amount of pressure per square inch is sustained by the ovum in the easiest class of natural labours, and thence to estimate the propelling power exerted in such cases.

It is well known that natural births are ever and anon occurring, in which the ovum is expelled whole, the membranes containing the liquor amnii continuing entire. Into this category many more cases would enter, were it not a generally-followed rule for the attendant to rupture the bag should it advance entire as far as the external parts. Again, as Dr Poppel has pointed out, the attentive observer of a series of easy natural labours has no difficulty in arriving at the conclusion, that in not a few cases the same force which ruptures the bag of membranes is able to, and actually does, complete the delivery.

Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 24 , Issue 3 , 1867 , pp. 639 - 651
Copyright
Copyright © Royal Society of Edinburgh 1867

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References

page 640 note * Water is preferable in these experiments to air, because, when it is employed, there is less violent action at the bursting of the membrane.

page 647 note * The same contractile force of the uterus at different periods of labour, or, to be more exact, at different dimensions of the uterus, will produce greater internal pressure, and, consequently, greater expulsive force, as the uterus is smaller (vide equation (2), p. 646); and, the amount of muscular contraction being supposed to be the same, there may be no sign to the attendant or patient of the increase of power. On the other hand, the application of the same principle shows, that, when the curvature of the extruded portion of the membranes is greatest, the difficulty of rupturing them is also greatest. This occurs when the extruded portion is hemispherical; and it is on this supposition that the numbers in column 22 are calculated.

page 650 note * Mémoires de l'Académie Impériale de Médecine. Tome xxvii, p. 90, &c. See also his Mémoire sur l'emploi de la Force in Obstétrique. Archives générales de Médecine: numéros Février et Mars 1867.

page 650 note † Traité complet d'Accouchements, p. 477.