Leonhard Euler, in his 1760 paper on curvature in the " Berlin Memoirs ", had considered, not the normals of the surface, but the normals of the plane sections through a particular normal, so that the question of the intersection of successive normals of the surface had never presented itself to him.
22.
Stereology exploits the fact that some 3-D quantities can be determined without 3-D reconstruction : for example, the 3-D volume of any object can be determined from the 2-D areas of its plane sections, without reconstructing the object . ( This means that stereology only works for certain quantities like volume, and not for other quantities ).
