350 



NORMAL HISTOLOGY. 



sclera, the iris, and the ciliary muscle, constitutes one of the most 

 important regions in the eye, not only with regard to its anatomical 

 details, but also in view of its practical clinical significance. 



As already described, the substantia propria of the cornea passes 

 directly into the ground-substance of the sclera ; in consequence of 

 the rearrangement of the tissue-elements of the two structures 

 taking place soonest in the superficial planes of the cornea, the line 

 of transformation becomes oblique, thereby producing an apparent 

 overlapping of the sclera in front, and a corresponding extension of 

 the cornea behind. 



The posterior elastic membrane, on reaching the corneal mar- 

 gin, splits up into a number of stiff homogeneous fibres, many of 

 which become attached to the base of the iris and constitute the liga- 

 mentum pectinatum iridis. By the union of the processes from 

 the iris and Descemet's membrane with the elastic fibres derived 

 from the anterior attachment of the ciliary muscle and a few bands 

 from the sclera, a reticulum of thin trabeculse is formed, which 

 occupies the angle between the cornea and the iris. This spongy 

 tissue constitutes an annular mass enclosing a system of intercom- 

 municating cavities, the spaces of Fontana. These clefts, lined 



FIG. 375. 



Section through irido-corneal angle of human eye, highly magnified : a, substantia propria 

 of cornea ; b, posterior limiting membrane, splitting at corneal margin into delicate lamellje 

 (d) ; c, endothelium continued over iris (i) ; f, elastic lamellae separating Schlemm's canal (S) 

 from spaces of Foniana (s, s) and giving attachment to fibres of ciliary muscle (h). 



by an imperfect layer of endothelium, are more conspicuous in the 

 eyes of some of the lower animals (horse, ox, pig, sheep), where 

 they are far better developed than in man. 



Within the sclera, close to its inner border and the corneal juncture, 



