54 2 MEMBRANE OF DEMOUHS. [sect. 224. 



membrane, accordingly, does not, therefore, terminate with a sharp 

 border, as is usually stated; but, as Reicliert first pointed out, 

 appears to pass altogether into a peculiar fibrous tissue. Opinions 

 are divided concerning the nature of these fibres ; for while Reichert 

 classifies them with connective tissue, and Brilcke regards them as 

 peculiar, Luschka declares that they belong to the so-called serous 

 fibres {i.e., fibres of elastic tissue). Bowman, again (Lectures, 

 p. 21), and Henle (Jahresb., 1852, p. 20), consider these fibres to 

 be partly of the nature of elastic tissue, partly of connective tissue, 

 while I myself view them as a form intermediate between these 

 two tissues. The truth is, that these fibres, where thev commence 

 on the membrane of Descemet, and in their continuations to the 

 wall of the canal of Schlemm, and to the ciliary muscles, seem to 

 belong to the category of elastic fibres from their dark contours, 

 their moderate thickness, and homogeneous appearance ; while the 

 parts which are continued upon the iris present a great resemblance, 

 morphologically, to connective tissue, viz., in their breadth (o - oo4'" 

 to 0'0i2'"), their paleness, and in having a well pronounced striated 

 appearance. This resemblance is so striking, that I formerly 

 (Zeitsch. f. tviss. Zool., i. p. 54), considered this portion of the 

 fibres as being a reticulate connective tissue. I must now, how- 

 ever, maintain, as in the first edition of the work (notwithstanding 

 the assertion of Henle, that the lig. iridis pectinotum is really 

 connective tissue), that these fibres in man differ widely from con- 

 nective tissue in their rigidity, in their reactions towards alkalies 

 and acids, and in their insolubility even on long boiling in water. 

 They are, indeed, closely allied to the elements of the zonule of 

 Zinn, which Henle himself does not regard as connective tissue. — 

 Nevertheless, I must observe, that in animals some of these fibres 

 do possess other characters than in man. Thus, in the rabbit, I 

 find, in their place, thick bundles of connective tissue with plasmatic 

 cells, or immature elastic elements, which are fixed in a pointed 

 manner into Descemet 1 s membrane, and thence expand and are lost 

 in the outer part of the iris ; in birds, on the other hand, the fibres 

 are distinctly those of elastic tissue. 



The epithelium of Demours's membrane, which is frequently 

 found destroyed by decomposition in the human subject, is a 

 simple layer, 0-002'" to o'003'" thick, of beautiful polygonal cells, 

 0006'" to co 1" in size, with extremely fine and pale granular 

 contents, and round nuclei, 0-003'" *° o - oo5'" in diameter. Towards 

 the border of the cornea the cells become smaller, and the epithe- 

 lium then terminates as a connected layer. On the other hand, 



