On the statics of pregnancy / by Matthews Duncan.

  • James Matthews Duncan
Date:
1855
Catalogue details

Licence: Public Domain Mark

Credit: On the statics of pregnancy / by Matthews Duncan. Source: Wellcome Collection.

    18/28 page 14
    tions of the foetuses. Till this be carefully done, we can base no reasonings upon the presentations of anencephalous chil¬ dren whose statical circumstances we do not know. Further, it has been attempted by Dubois and others^ to shew that the position assumed by the foetus when immersed in a fluid, or rather when allowed to fall through a mass of water, is inconsistent with the gravitation theory. It has been shown, in these ill-devised experiments, that the part of the foetus which reaches the bottom of the vessel first is not the head, as these authors fancv should be the case if the gravitation theory were correct, but is the shoulder. But the fact is, that the line of descent through a fluid of nearly equal specific gravity with the body descending, is in the case of the foetus, as in all other bodies, not a vertical line in the long axis of the body, drawn from what is the abso¬ lutely heaviest part, but a vertical line from the centre of buoyancy to the centre of gravity. (See Fig. 10.) The same fact is expressed in the hydrostatical principle, that a body floating and immersed is in stablest equilibrium when the centre of gravity is vertically below the centre of buoyancy, —i.e.j the centre of gravity of the fluid displaced. These very experiments, and numerous other facts, show that the centre of gravity is much nearer the cranium in the foetus, and especially when in the foetal attitude, than it is in the adult; that it is, in fact, near the upper part of the back, and nearer the posterior than the anterior surface of the child. The centre of buoyancy of the foetus will be very nearly the centre of the oval figure which encircles the foetus. (See Fig. 10.) Both these centres will be liable to constant variations with the varying dimensions and specific weights of different parts of different foetuses, and with the varying at ti¬ tudes of the parts of the same foetus. But allowing for every variation, it is evident, that if these two centres be in the case of the foetus placed in the same vertical line, the foetus will be inclined obliquely to the horizon, as we find it to be in its ordinary position.^ The experiments of Dubois and Simpson, involving as they do, rapid motion in falling through water, are fitted to afford results of a very small degree of value or reliability. So far as they go, they point to the fact of the descent of the foetus, shoulder lowest, or, to speak more correctly, following the 1 When a human fcetus of the latter months” (says Dr Simpson) is j)laced experimentally in fluid, in descending through the fluid the head does not turn and fall first to the bottom of the containing vessel, as the theory of gravitation takes for granted that it would. Thus, if a dead new-born fcetus be plunged into water, contained either in a vessel shaped like the uterus, or in a large bath, the part which gravitates and strikes the bottom of the vessel or bath first, is
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