292 DETAILED SYNTHESIS. 



light acts freely upon them, and being a deep brown near 

 the sclerotic. This part of the eye is called the choroid 

 coat. 



744. THE CHOROID DOES NOT REACH FORWARD AS FAR 

 AS THE SCLEROTIC, is loosely connected with it through- 

 out by Blood-tubes and sinewy fibres, that become more 

 dense at the front part of the choroid, and more inti- 

 mately connected with the sclerotic; thus forming the 

 ciliary body (4), in which the capillary vessels are found 

 in greatly diminished numbers. (See 1 746.) 



745. THE PROPER NERVOUS STRUCTURE OR RETINA 

 OF THE EYE exists in five layers: 1st, a layer of columnar 

 cells (membrane of Jacobi), resting against the choroid ; 

 2d, a granular layer (like that of the ganglia) ; within 

 that is, 3d, a layer of caudate cells, connected with, 4th, 

 the nervous fibres, covered with, 5th, a layer of struc- 

 tureless membrane, like basement membrane. 



746. THE RETINA does not EXTEND QUITE AS FAR 

 AS THE CHOROID, the capillary vessels of which diminish 

 rapidly in number as soon as no longer necessary in 

 large numbers to furnish nutriment to the retina. 



747. THE NERVOUS FIBRES OF THE RETINA are mil- 

 lions in number, some terminating almost the instant 

 they enter the eye, in caudate cells near the entrance, 

 others extending to the last row of cells at the front 

 border of the retina. 



748. Remark. THE NERTE-FIBRES TURN BACK to connect with the 

 cells forming the layer next behind the fibre-layer. They do not present 

 their points toward the concavity of the eye, as for certain reasons has 

 been represented hi several of the figures illustrating the eye, nor do 

 they terminate in points, but in or at the caudate cells, with which they 

 are continuous. 



749. ALL THE LAYERS OF THE RETINA are transpar- 

 ent, as can be judged from the fact that the pupil of 

 the eye appears black, owing to our looking through the 



744. What results since ? 745. What said of ? 746. Does f 747. What 

 Wid of ? 748. Why do ? 749. What true of ? Effect of choroid. 



