The formation of this layer, superficially seen, corresponds to the simple denaturation skin [membrane] of a solution of a native protein, and this rests on a colloid-chemical surface-adsorption resulting in a [local] concentration and subsequent systemic grouping (similar to coagulation). [Adsorption is attraction of a substance by a body, without this substance being imbibed by it. Absorption, on the other hand, is the same phenomenon of attraction, but now with imbibition.] But the basic phenomenon can be seen in any boundary phase of liquids [for example oil and water, - emulsion] or solutions [permanent suspension of solid particles in a liquid, - colloidal solution]. The boundary layer, as a result of the unsymmetric action of intermolecular forces being structured orientationally, of a liquid is -- individually-compositionally -- as a result of constant molecular exchange, only of a statistical nature. Here only unspecific summational and superpositional effects are possible at all, i.e. a liquid of any size [that is, bulk liquid], and especially its boundary layer, is, it is true, something else than the single molecule, from a multitude of which that layer is composed, but nevertheless still something similar. The new qualities rather direct reduce to the individual molecule, and may derived from it directly. [So, for example, surfactant molecules (soap molecules, see Introduction above]. They lump up together with their equivalent ends, and may in this way form micelles separating inside from outside.].
In living substance this is quite different. Here also the surface layer has -- despite a supposed weak to and fro swinging of the vital phase boundary [here Müller places a question mark] as well as metabolic exchanges -- an organ-like enduring nature. [For here it is about the boundary between the living and non-living state.]
Just as in the case of the surface layer of a liquid, one should, to begin with, also imagine the denaturation membrane as coarse-chemically equivalent to, or identical with, the substrate lying at its [the denaturation membrane's] base, being enclosed by it [i.e. by the denaturation membrane], and most closely connected with it, and [equivalent to, or identical with] -- unlike a rubber skin -- a tension independent of size. Only roughly we here have the same chemical composition, because one, neglecting many substances of the cell content, takes into account a homogeneous filling-up with precisely that substance from which the membrane has formed. Moreover, this only applies to reversible spontaneous membranes, whereas permanent membranes (but still not to confuse with cell walls and the like) should be considered under the view of molecular differentiation.
Not considering a possible reversibility, the difference between non-living membrane and living internal substance is fundamental and enormous.