Chapter 1 19 hair cortex. These are contained in the mesocortex and, as the name implies, they are intermediate in character between cells of the ortho- and para-cortex.46 They are not so readily recognized according to the amount of intermacrofibrillar matrix separating the cell’s macrofibrils but rather by the fine structural details in their macrofibrils compared with those found in the other two cortical cell types.40 Keratin composite: Sections of hair for the electron microscope stained with ammoniacal silver (or indeed with several other heavy metal compounds) reveal the macrofibrils of the cortex contain significantly large amounts of protein-bound cystine (c.f. Figures 9 and 10). More particularly the transverse section of each macrofibril consists entirely of a two-phase keratin composite of unstained rods of relatively low cystine content embedded in a stained protein matrix of high cystine content (Figure 10). This two-phase composition of the hair’s major component is reflected by Figure 10. High magnification electron micrograph of a portion of paracortex showing the keratin composite consisting of intermediate filaments embedded in a high cystine protein matrix.