Transverse Striations in Extended Wool Fibers

Abstract

Transverse striations can be seen in extended wool fibers under the optical microscope. This phenomenon has been further investigated by electron microscopy and other means. The optical effect arises from groups of small primary striations. At low over-all extensions, only a few striated regions can be seen. The local extension in such a region can be several times the over-all extension. The extension in a primary striation within a striated region would be still higher. Adjacent unstriated regions are at extensions lower than the over-all value. It is thought that the unfolding of α-keratin and formation of β-keratin during mechanical yield takes place in primary striations. Individual striations can have lateral dimensions large enough to occupy the whole cross section of a cortical cell.