Hyaline infiltration of the eyelid.

The term "hyaline degeneration ", first employed by von Recklinghausen (1883), denotes a physical state rather than a chemical composition. " Hyalin" includes a heterogenous group of substances which share the properties of being translucent, refractile, and structureless (Gk, hyalos-glass). They stain readily with acid dyes, are resistant to strong acids and alkalis, and are all of a protein nature. The term is applicable to such apparently unrelated conditions as the arterial sub-endothelial thickening of arteriosclerosis, scar tissue, stromal degeneration in tumours, the degenerative changes of the islets of the diabetic pancreas, and the corpora amylacea of the brain and prostate. It is clear that this wide term should also include " amyloid" (Gk, amylon-starch, eidos-form), a hyaline substance as defined above which is only entitled to a special name on account of its characteristic anatomical distribution, its typical staining reactions, and the fact that it is the only one of these substances having a known chemical composition. It is now generally agreed that amyloid is a glyco-protein, in which the carbohydrate ester, chondroitin sulphuric acid, has become attached to a globulin. It is probable, however, that its chemical composition varies, for the staining reactions are by no means constant. Indeed, Raehlmann (1881, 1882) and Kubli (1881) regarded hyalin as the precursor of amyloid; others, who distinguish strongly between the two, admit that they form related although independent end-products of kindred processes (Duke-Elder, 1938). Schmiedeberg (1920) also considers hyalin to represent a transition