THE EYE. 729 



bundles of connective tissue or elastic fibres, are occasionally visible, 

 given off from it, and penetrating the cornea to a certain distance, where 

 they are lost. 



The membrane of Descemet or Demours, also termed the membrane 

 of the aqueous humor (memb. Descemeti, s. Demoursii s. humoris aquei) 

 (Fig. 296 d), consists of an elastic membrane rather laxly attached to 

 the corneal tissue the proper membrane of Descemet ^posterior elastic 

 lamina of the cornea, Bowman}, and of an epithelium on its inner sur- 

 face. The former is as clear as glass, brilliant, quite structureless, 

 easily lacerable, though tolerably firm, and so elastic, that when it is 

 raised from the cornea by the scalpel and forceps, by boiling in water, 

 or by maceration in alkalies, under which treatment, as under reagents 

 in general, it does not lose its transparency, it always rolls up strongly 

 and towards the front. Towards the border of the cornea, the mem- 

 brane of Descemet, which is O006-0-OOS of a line thick, and in chemi- 

 cal properties approaches the homogeneous membranes ( 16), passes 

 into a peculiar system of fibres, first accurately described by Bowman. 

 This set of fibres commences at a short distance from the margin of the 

 cornea on the anterior surface of the membrane of Descemet (Fig. 296 </), 

 as an elongated network of fine fibrils, like the finer elastic fibrils, after- 

 wards gradually increasing in thickness, until at the very margin of the 

 cornea, the whole thickness of the membrane of Descemet is broke*n 

 up into a network of thicker fibres and trabeculce, which turn over upon 

 the border of the iris (Fig. 296 i), and are blended with its anterior 

 surface. Consequently, the membrane of Descemet does not cease, as 

 is usually stated, with a free border, but, on the contrary, is continued 

 (Fig. 296 /) all round the anterior chamber, by numerous free processes 

 passing across it, upon the iris. The elements of this ligamentum 

 iridis pectinatum, as it is termed by Huek [pillars of the iris, Bowman], 

 and which, according to Luschka, is much more distinct in the eyes of 

 certain animals (Dog, for instance) than in Man, were formerly 

 (" Zeitsch. f. wiss. Zool.," L, p. 54) referred by me to reticular connec- 

 tive tissue, at a time when I was acquainted with their form but not 

 with their reactions; now, however, I should rather be inclined to 

 describe them as an intermediate form between the connective and 

 elastic tissues. The bundles in question correspond with those of con- 

 nective tissue, in their width (0-004-0-012 of a line) and paleness, and 

 also in the circumstance that still finer fibrils are usually to be distin- 

 guished in them, whilst in their rigidity and chemical reactions they 

 approach the elastic tissue and the membrane of Descemet itself, of 

 which latter, though probably differing from it genetically, they are, in 

 the adult at any rate, an integral constituent. 



The epithelium of the " membrane of Demours" (Fig. 296 e), which, 

 in Man, frequently does not retain the perfect condition, is a single 

 layer, 0-002-0-003 of a line thick, of well-formed, polygonal cells, 



