THE EYE. 



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is found to consist of ten layers, which are named from within outward as 

 fellows : 



1. Membrana limitans interna. 



2. Fibrous layer, consisting of nerve-fibres. 



3. Vesicular layer, consisting of nerve-cells. 



4. Inner molecular, or granular, layer. 



5. Inner nuclear layer. 



6. Outer molecular, or granular, layer. 



7. Outer nuclear layer. 



8. Membrana limitans externa. 



9. Layer of rods and cones (Jacob's membrane). 

 10. Pigmentary layer. 



1. The membrana limitans interna is the most internal layer of the retina, and 

 is in contact with the hyaloid membrane of the vitreous humor. It is derived from 

 the supporting framework of the retina, with which tissue it will be described. 



FIG. 532. The arteria centralis retina, yellow spot, etc., the anterior half of the eyeball being removed. 

 (Enlarged.) 



2. The fibrous layer is made up of nerve-fibres, the direct continuation of the 

 fibres of the optic nerve. This nerve therefore passes through all the other layers 

 of the retina, except the one previously mentioned, to reach its destination in the 

 fibrous layer. As the nerve passes through the lamina cribrosa of the sclerotic 

 coat the fibres of which it is composed lay aside their medullary sheaths and 

 are continued onward, through the choroid and retina, as simple axis-cylinders. 

 When these non-medullated fibres reach the internal surface of the retina, they 

 radiate from their point of entrance over the surface of the retina, grouped in 

 bundles, and in many places, according to Michel, arranged in plexuses. The 

 layer is thickest at the optic nerve entrance, and gradually diminishes in thick- 

 ness toward the ora serrata. 



3. The vesicular layer consists of a single layer of large ganglion-cells, except 

 in the macula lutea, where there are several layers. The cells are somewhat flask- 

 shaped ; their rounded internal margin resting on the preceding layer, and sending 

 off a single process, which is prolonged into the fibrous layer, and is believed to be 

 continuous with a nerve-fibre. From the opposite extremity of the cell one or 

 more thicker processes extend into the inner molecular layer, where they divide 

 dichotomously and become lost in its reticulum, or, according to some, pass 

 through this layer to reach the inner nuclear layer. 



4. The inner molecular layer consists of a stratum of granular-looking sub- 

 stance, from which circumstance it is sometimes called the " inner granular" layer. 



