INTRODUCTION TO SOCIOLOGY 617
Laplace, every liquid withdrawn from the capillary forces exer- cises upon itself, by virtue of its cohesion, a normal pressure on the free surface, a pressure which is equivalent to a constant quantity augmented by the product of the average curvature of the surface, at the point considered, by a constant factor which depends upon the nature of the liquid.
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The second theorem, stated in the memoir of Z. Plateau upon the phenomena which result from the withdrawal of a free liquid mass from the influence of gravitation, shows us that the mass thus left to itself assumes the form of a sphere, which then constitutes a form of equilibrium. In fact, in a sphere, since the curvature is the same on all sides, the pressure which is mentioned in the theorem of Laplace is exercised on all sides, and the mass is in equilibrium.
The sphere is, then, a state of equilibrium between certain internal forces and other external forces. Applying the princi- ple that a spherical surface limits the maximum volume, and the two theorems of Laplace and Plateau to inferior organisms, we ascertain, in the first place, that the conditions required for the application of these principles are to be found in organisms. According to Hackel, organisms in general are largely composed of water ; the body of a man contains 70 per cent. This large proportion of water is especially remarkable in the case of the jelley-fish, which, according to the same author, contains 99 per cent. One may, then, without sensible error, liken such an organism to a liquid mass. Moreover, these inferior organisms floating in the waters of the ocean are removed from the influ- ence of gravity. The principle of the maximum volume in a limited surface, and the two theorems of Laplace and Plateau, are, then, applicable to the inferior organisms. That of the maxi- mum volume is in direct correlation with the natural tendency of matter to store the most life possible within the least surface. We may conclude that the surface limiting the elementary organic matter is clearly the result of an equilibration between internal forces and the most general forces of the environment.
