a1 Biology Department, Wool Industries Research Association.
The mammalian hair-fibre, together with the “inner root-sheath” (i.e. the axial layers of the follicle wall), grows upward by a proximal addition of cells. Changes in the inner root-sheath are responsible for the final shape and surface sculpture of the fibre. At its distal limit the inner root-sheath disintegrates owing to the effect of a de-keratinizing chemical agent.
A bent, undulated, or “crimped” fibre is due to a differentiated progress of the changes leading to keratinization of the “fibre cortex”. The cells which give rise to a “medulla” are different chemically and less compressible than cortical cells.
(Received September 11 1948)
(Revised November 30 1950)