Recklinghausen has introduced this term to designate conditions in which a clear homogeneous substance of a vitreous appearance is present, which does not yield the reactions of amyloid substance or mucin. This Hyalin has special reactions to some staining agents, being deeply coloured by most of the acid dyes. Thus carmine, picro-carmine, and to a less extent, haematoxyline, eosine, and acid fuchsine stain it deeply. It is an inert substance and its presence implies that the structures involved are obsolete if not dead. The substance is insoluble in water and alcohol, and is unaffected by acids and alkalies. It is insoluble in the juices of the tissues; at most, swells up when acted on by them and remains as an inert substance. Like amyloid matter and mucin, it arises chiefly by transformation of cells, but there are some conditions included by Recklinghausen, in which this can hardly be said to be the case.
It is not asserted by Recklinghausen that hyalin has a determinate chemical constitution, and there are probably many different conditions included in the name. The following is a list of the conditions included under hyaline degeneration: - (1) Colloid degeneration; (2) Some instances of coagulation-necrosis, and more particularly the waxy degeneration of muscle; (3) Tube casts in the kidneys (hyaline cylinders) and similar structures met with in inflammations in the ducts of the sweat glands, and in the ovarian follicles; (4) Hyaline matters in many tumours, as in lymphomas, sarcomas, and cancers, as well as in tubercles; (5) On mucous membranes, forming the main constituent of diphtheritic membranes; (6) In thrombi and fibrinous exudations, where the fibrine, at first forming a net-work, becomes converted into a hyaline homogeneous material; the thrombi in aneurysms often assume this character; (7) In the eye as prominences in the hyaloid membrane.
Recklinghausen, Allg. Path., p. 404.