Textiles 87
located within the amorphous bulk of the keratin, comprise the proteinaceous
regions of the cortical cells. The amorphous matrix itself is principally sta-
bilised by the large number of disulfide bridges, which link proximate cyst-
eine residues. The cortex can be further divided into two general regions, the
orthocortex and the paracortex, the former containing more crystalline fibrils
and the latter more largely composed of amorphous material.
Finally, depending on the species from which the wool is taken, a medulla –
a hollow, air-filled cavity – may be present at the centre of the fibre. This feature
is generally found only in coarser fibres, and may take a number of different
forms, ranging from a continuous unbroken channel (e.g.many sheep’s wool
fibres) to interrupted, lattice-like structures (e.g.rabbit fur).
5.2 Wool as a Textile Fibre
Wool lacks the mechanical strength of silk, due to its cellular nature and lesser
degree of crystallinity. However, these factors also give it a greater extensibility
Figure 24Typical wool fibres
Figure 25Schematic of an -helix