Chapter 1 15 If we consider the β-layers to be associated with the cuticle cells on either side of the CMC, then the “inner β-layer” is defined as being on the inner-facing aspect of one cuticle cell, whilst the “outer β-layer” is on the outer-facing aspect of the adjacent cuticle cell.12 The lack of staining of the β-layers with heavy element stains of the type used in electron microscopy points to their being composed of lipids. There is strong evidence to believe the outer β-layer contains covalently bound 18-MEA.33 In this respect it is worth bearing in mind that 18-MEA, known to be present at the outer exposed surface of the hair cuticle, represents the outer β-layer of the outermost cuticle cell. The inner β-layer probably also contains covalently bound lipids but not 18-MEA. Further details of the precise composition of the β-layers in the CMC between the cuticle cells remain to be determined, albeit there is a strong possibility all the lipids contained in them are covalently bound to the adjacent material. The chemistry of the δ-layer remains uncertain. That it doesn’t contain cystine is confirmed by its lack of staining in sections treated for a short duration with ammoniacal silver. Interestingly globular silver is deposited in this component in small amounts when sections are briefly treated with periodate and then with silver-methenamine reagent.34 Such staining probably arises from the scission of vicinal diols of polysaccharidic components to yield aldehydes that subsequently reduce the silver reagent to a globular metallic form. PTA staining of the δ-layer continues to be intense even in sections where free amino groups have been eliminated by reacting the hair beforehand with dinitrofluorobenzene. If, as seems highly likely, polysaccharides are present in the δ-layer, the positive PTA staining (carried out at a pH 1.8) could well be due to the binding of the phosphotungstate anion at protonated hydroxyl groups of sugar residues. In this connection Orwin35 found a diffuse layer of extracellular glycoprotein (or glycocalyx) around the cells of the wool follicle of a type commonly associated with the surfaces of many other epithelial cells. It is not unreasonable to suppose a similar coating around the early cuticle cells has been compressed