SECT. 224.] MEMBRANE OF DEMOURS. 54 1 



CT003"' to 0"004'" in thickness, and is especially distinct upon 

 perpendicular sections, and when horizontal sections are folded 

 together after the addition of alkalies. This lamella, however, is 

 far from being so sharply marked off from the proper cornea as 

 Descemet's membrane, nor does it appear to have the same signifi- 

 cation as that membrane, being, perhaps, nothing else than the 

 remains of the vascular lamina which previously existed in the 

 corneal conjunctiva. — Curved fibres, like rigid bundles of con- 

 nective tissue or elastic fibres, are occasionally seen to pass off 

 from this conjunctival membrane for some distance into the cornea, 

 where they are lost. 



The membrane of Descemet, or Demours, called also memhrana 

 humoris aquei, consists of an elastic membrane, rather loosely 

 attached to the tissue of the cornea, and of an epithelium upon the 

 inner surface thereof. The former elastic layer, which is the proper 

 membrane of Descemet, is clear like glass, brilliant, perfectly struc- 

 tureless, and can be readily torn; it is, however, tolerably firm, 

 and so elastic, that when it is separated from the cornea by the 

 knife and foi'ceps, or by boiling in water, or by maceration in 

 alkalies, it invariably curls up strongly, with a direction forwards. 

 By this treatment, as by re-agents in general, the membrane is not 

 deprived of its transparency ; it appears to be identical in its che- 

 mical characters with the other homogeneous membranes. The 

 thickness of Descemet's membrane amounts to 0"Oo6'" to 0008'", 

 and towards the borders of the cornea, it passes into a peculiar 

 system of fibres, which were first observed by Reichert, and de- 

 scribed more at length by Bowman. This system of fibres com- 

 mences at a small distance from the border of the cornea at the 

 anterior surface of Descemet' s membrane, and first forms an elon- 

 gated network of fine fibrillar, like fine elastic fibrils ; these then 

 become gradually denser, till, at the border of the cornea itself, 

 Descemet's membrane has broken up in its entire thickness into a 

 network of thick fibres and trabecular, which divides into three 

 portions. The one part turns round in the whole circumference 

 of the anterior chamber of the eye in the form of numerous pro- 

 cesses, which pass freely through this chamber upon the anterior 

 border of the iris; these constitute the lig. iridis pectinatiim, and 

 coalesce with the anterior parts of this structure. Another portion 

 passes into the ciliary ligament, or rather, into the musculus 

 ciliaris; and the remainder of the network prolonged from 

 Descemet's membrane is lost in the inner wall of the canal of 

 Schlemm (see below, under the account of the uvea). Descemet's 



