The distribution of salts in living matter is supposed, in the current conception of the subject, to be on the whole the same as in ordinary fluids. Living matter is generally regarded as a semi-fluid, semi-viscid material in which the conditions, though not fully typical of those which obtain in a fluid like water, are, nevertheless, such as to allow the substances that are dissolved in it to be distributed uniformly throughout it. The only obstacle to this distribution may be presented by a membrane such, for example, as that which encloses or surrounds the cell nucleus. Elsewhere throughout the cytoplasm there is, it is believed, a free play of the force that determines the diffusion of the substances dissolved, until uniformity in their dispersion obtains throughout the volume occupied by the cytoplasm. This force is that postulated in the van't Hoff theory of solutions extended to include the arrhenius theory of dissociation. In this composite theory, as is well known, the material dissolved in a fluid is supposed to be in a state analogous to that of a gas, that is, in as rarefied a condition as if its molecules were isolated from each other and occupying alone the volume filled by the solution itself. The molecules of the solute and their ions, when they are dissociated, are thus supposed to be in translational motion, and the resulting pressure—the osmotic pressure—which they give, acts on the surfaces enclosing the fluid as the molecules of a typical gas act on the walls confining it. At every point in the system there would be, on this view, the same pressure and, in consequence, the number of molecules per given volume of the solution in any portion of it would be uniform.