THE EYE AND ITS APPENDAGES. 



347 



retina. The various components of the iris and their morphological 

 relations may be grouped as follows : 



1 . Anterior endothelium. 



2. Anterior boundary layer, ~) Continuation of the tissues of the 



3. Vascular stroma-layer, > uveal tract proper, constituting 



4. Posterior boundary layer, j the stroma-zone. 



a. Anterior layer of pig- ' 

 mented spindle - cells 

 representing outer 

 layer 



b. Posterior layer of pig- 

 mented polygonal cells 

 representing inner 



. layer 



The anterior endothelium consists of a single layer of thin nu- 

 cleated polygonal plates, the direct prolongation of the corneal 

 endothelium. The protoplasm of the cells is finely granular, but 

 always free from pigment. 



The anterior boundary layer is formed by modification of the 

 foremost stratum of the iris-stroma; the connective tissue consti- 



5. Pigment-layer, 



of OPTIC VESICLE. 



Section through part of iris and lens, from human eye : /, iris ; a, anterior 

 endothelium; t, anterior boundary layer; c, vascular stroma; d, posterior 

 boundary layer ; e, pigment-layer continued as far as g on pupillary margin 

 (P) ; f t cut circular muscle-bundles of sphincter ; L, surface of crystalline 

 lens ; h, anterior lens capsule, with anterior epithelium beneath ; i, tissue of 

 lens. 



tuting this layer resembles the reticular tissue of lymphatic struct- 

 ures, comprising several layers of net-works within the interspaces 

 of which lie lymphoid cells in greater or less profusion. 



The vascular stroma constitutes the chief mass of the iris, and, 

 in addition to its numerous blood-vessels, contains involuntary 



