Epidermis can be classified as a multilayer optical periodic milieu.
Thus, Mikhailov I.N. has showed in his researches  the multiple
layers of human epidermis; in our researches we have explored the
multiple layers of fish scales, tortoise-shell scutes and bird
feathers . Picture 1 shows the fish scale transverse section. We
can clearly see the multilayered structure and also note the optical
density of different epidermis layers.
Pic.1 Cross section of fish scale On the scale surface we can
distinctly see the system of lines and figures. Picture 2 shows the
diagram of these figures that divide the scale surface into at least
4 parts: A, B, C, D.
Pic.2 Layout view of scale surface
We can see these lines on the photographs of the surfaces of two real scales (Pic.3).
Pic.3 Photographs of scales
Through all these areas passes the system of looped concentric
ellipse-like lines, enclosed into each other with a spacing
approximately 20-40 mcm. There are more than a hundred of such
ellipsoids. The enlarged segments of these ellipsoids are shown in
the picture 4.
Pic.4 Ellipse-like lines
The "A" zone is formed by crossing of two groups of lines - the
ones formed by ellipsoids and the vertical (radial) ones directed to
the center of the scale surface. As the result they form a net (grid)
observed from both sides of the scale. This grid spacing on the one
hand is determined by the grid spacing of the ellipsoids (20-40mcm)
and on the other hand by the distance between the radial lines
(100-200mcm). Sometimes in this area we can see segments of the grid
with large square cells with the spacing determined by the distance
between radial lines: 150 ? 150mcm as it is shown in the picture 5.
The "B" zone is formed by the set of lines in the ellipsoid
system. The "C" zone is a matt ellipse in the center of the scale
surface. The "D" zone attracts a particular interest. It is a gray
area, a jelly-like membrane connected with the solid part of the
scale. Picture 6 shows the 200 times enlarged structure of this area.
Pic.6 "Gray Area"
In the picture we can pay attention to the assembly of the other
neuro-like formations connected to each other. Some of them have
elements that resemble nucleuses. Picture 7 shows a single
Pic.7 Single neuro-like formation
By painting the scale silver we have managed to discover at least two types of connections between these structures: unregulated connections that form areas tightly filled with these neuro-like formations and resembling gray matter,
and a system of connections forming the net structure shown in the picture 8.
Pic.8 Neuro-like net-structure
The spacing of this net is comparable with the grid spacing in the "A" zone. We need to mention here that the solid base of the gray zone "D" has the picture of the lines and figures very similar to the ones in the "A" zone (Pic.2-3).
The gray membrane (the "D" zone) is morphologically and functionally connected through the skin with the body of the fish. Picture 9 presents the neurons in this zone close to its border with the skin. We see the neuron myelin sheath. This indicates on nervous connection between the gray membrane and the central nervous formations of the fish.
Pic.9. Boundary neurons between skin and "Gray Area"
Picture 10 schematically displays the system of two interconnected scales in two dimensions - the section of the fish body.
Pic.10. Body surface fragment consisting of a few scales
In this picture we see that one side of every scale (the "A" zone)
covers the gray membrane of the neighbouring scale (the "D" zone).
As the result, this area that includes the set of neuro-like
formations connected in a certain way is located between two optical
solid transparent structures with reticulated surface: the one from
the neighbouring scale (the "A" zone) and the one from the scale it
is connected to. One side of the gray membrane is joined to the skin.
The connection with the electron-ion millieu and central nervous
formations of the fish is likely to be accomplished through this
joint. The middle matted part (the "Ѧquot; zone) resembles an optical
formation that directly connects the environment and the body of the
fish. So, the surface of the fish body can be presented as a mosaic
epidermal structure where two types of the gray areas interleave -
the gray ones that virtually are three-layered formations with the
system of neuro-like elements in its middle and the light ones that
are transparent single-layered areas with matted ellipse in its
center (the "Ѧquot; zone).