The pleura is a membrane that surrounds the lungs of mammals. Presumably, the phrase means that the surface of the pleura was found to be normal in an examination.
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There is no such expression. The normal to a surface, at a given point is the radius of curvature of the surface, at that point.
The normal vector to the surface is a radius at the point of interest.
The mean of a standard normal distribution is 0.
A curved surface area can be described as one where the gradient of the normal to the surface changes smoothly from point to point.
Matte proof coins are special proofs that have a grainy "sandblasted" look on the surface. Matte proof coins were sometimes made in the early part of the 1900's. Normal proof coins have a mirror like brilliant surface.