STRUCTURE AND NUTRITION OF THE CORNEA. 263 



titude of corpuscles, the fusion of the walls of the cells with the hyaline sub- 

 stance, and the rupture of the cells, whereby the contained corpuscles are set 

 tree. At the same time, the hyaline substance gradually comes more and more 

 fo present a fibrous appearance ; and the whole may thus degenerate, until 

 scarcely a trace of the original cartilaginous structure is left. The progress of 

 disease is sometimes arrested, however ; and a natural cure tends to take place, 

 by the development of a white fibrous membrane from the intercellular sub- 

 stance, with which yellow fibres are intermingled that are derived from the 

 cell-nuclei. And it is in this way that the attempt is made to bring together 

 the two edges of an incised wound, or to fill up loss of substance occasioned by 

 the actual removal of Cartilaginous tissue; for it does not appear that any 

 power exists in Cartilage to generate new tissue of its own kind for such pur- 

 poses. Many weeks or even months are required by this process; and hence 

 some observers have altogether denied that any reunion of incised wounds of 

 Cartilage, or any filling up of breaches of surface, ever takes place. (See Redfern, 

 Op. cit.) It is curious that fractures of certain cartilages (as those of the ribs) 

 are commonly repaired by osseous union; a fact which seems to have reference 

 to the normal ossification of these cartilages among many of the lower animals, 

 and to their not unfrequent conversion into bone in the latter period of life in 

 the Human subject. 



254. The Cornea of the eye bears but a slight resemblance to Cartilage in 

 regard to its intimate structure, though it corresponds with it closely in the mode 

 of its nutrition. Besides its anterior or conjunctival layer, which consists of 

 three or four strata of epithelium-cells, and its posterior layer of cells constituting 

 the epithelium of the aqueous humor, the Cornea proper has been shown by 

 Mr. Bowman 1 to consist of three layers, which he designates respectively as the 

 " anterior elastic lamina/' the "lamellated cornea," and the " posterior elastic 

 lamina." The lamellated tissue which makes up the principal substance of the 



cornea, consists of superposed lamellae (Fig. 55), which are individually of no 



3S up 1 

 .55), 



Vertical section of the Sclerotic and Cornea, showing the continuity of their tissue between the dotted lines, 

 a. Cornea, b. Sclerotic. In the cornea, the tubular spaces are seen cut through, and in the sclerotic, the 

 irregular areolse. Cell-nuclei, as at c, are seen scattered throughout, rendered more plain by acetic acid. 

 Magnified 320 diameters. 



great extent, but are connected together both horizontally and vertically by 

 membranous prolongations ; about sixty of these lamellae are estimated to inter- 

 vene between any two corresponding spots on the opposite surfaces of the tissue ; 

 and each of them seems, when highly magnified, to present a faintly fibrous tex- 



1 " Lectures on the Parts concerned in the Operations on the Eye," pp. 10-22, and Todd 

 and Bowman's "Physiological Anatomy," p. 404, Am. Ed. 



