The substantia propria is fibrous, tough, unyielding, and perfectly transparent. It is composed of about sixty flattened lamellæ, superimposed one on another. These lamellæ are made up of bundles of modified connective tissue, the fibers of which are directly continuous with those of the sclera. The fibers of each lamella are for the most part parallel with one another, but at right angles to those of adjacent lamellæ. Fibers, however, frequently pass from one lamella to the next.
The lamellæ are connected with each other by an interstitial cement substance, in which are spaces, the corneal spaces. These are stellate in shape and communicate with one another by numerous offsets. Each contains a cell, the corneal corpuscle, resembling in form the space in which it is lodged, but not entirely filling it.