  Coordinates are introduced on the Mf [manifold] in the most direct  way through the mapping onto the number space, in such a way, that  all coordinates, which arise through one-to-one continuous  transformations, are equally possible. With this the coordinate  concept breaks loose from all special constructions to which it was bound earlier in geometry. In the language of relativity this  means: The coordinates are not measured, their  values are not read off from real measuring rods which react in a definite way to physical fields and the metrical structure,  rather they are a priori placed in the world arbitrarily, in order to characterize those physical fields including the metric structure numerically. The metric structure becomes through  this, so to speak, freed from space; it becomes an existing field  within the remaining structure-less space. Through this, space as  form of appearance contrasts more clearly with its real content: The  content is measured after the form is arbitrarily related to   coordinates.[109] 