The denaturation membrane which we here mean is principally present qua natural law. So one doesn't need to dispute about it in the presence of contradictory findings or non-demonstrability in many cases. In its most simple form of only low-molecular size perpendicular to the surface (and thus the so-called thickness) it is, of course invisible. Almost always a functional thickening and intussusceptional stiffening [i.e. a stiffening as a result of insertion of materials] seems to take place, an intussusceptional stiffening as a result of automatic or stimulated adsorption (at least in cellular life, having at its disposal the relevant insertion materials), as a result of which, however, also the reversibility is harmed. On the other hand, it can now be recognized easier [than in its most simplest form]. That, what is indicated as "skin" often is already functionally organicly a further development. One should be correspondingly cautious then in drawing conclusions, and, of course, certainly so when it is about markedly artificial products which are generated crudely experimentally only.
Evidently, many fixational [mounting] and coloring structures (in dead tissue) were artificial forms of denaturation. Anyway, one may assume that their formation is based on normal micro-histological structures of the living tissue.
What precisely in vital-coloring is actually colored, one can hardly say. It is certainly not the truly essentially living substance. The dye can only be present "between" it.
According to S. Strugger acridine-orange is very useful as fluorescence indicator in vital-coloration. In vital-colored cells the various cell components fluoresce widely differently, for example membrane : red, cell nucleus : green, cytoplasm : dark green brown. So, apparently, basically : living "protein" green, dead protein red. In all this it is totally indifferent in which way the death of the cell has taken place (chemically, thermically, or mechanically).
The fluorescent glow may directly taken to be a criterium of the living state of the cell, respectively its death. However, other authors have noted that one should take into account the point in time in all this. As a result of secondary and tertiary effects such as swelling phenomena and dye diffusions, also dead cells may lose again the red fluorescence acquired in dying, and fluoresce green as do living cells.