THE EYE. 



into small bundles, which, compressed laterally, intercommunicate and form a 

 delicate web with narrow elongated meshes (fig. 49). At the yellow spot this layer 

 is almost wanting, and indeed it ceases at the central fovea, but elsewhere it forms 

 a continuous stratum, gradually diminishing in thickness in front, interrupted only 

 by the enlarged ends of the fibres of Miiller to be afterwards described (fig. 48, 1). 

 The nerve-bundles, as well as the cells of the next layer, are partially supported by 

 neuroglia-cells (spider-cells). Most of the fibres are continuous with the axis- 

 cylinder processes of the cells of the next layer (fig. 50, i.), but some are con- 

 tinued through the second and third layers, and end by ramifying either in the 

 inner molecular layer or amongst the elements of the fourth layer (inner granules), 

 the terminations being frequently somewhat knobbed or enlarged (fig. 50, i., m). 



2. Ganglionic layer. Immediately external to the nerve-fibre layer is a 

 stratum of nerve-cells (fig. 48, 2), having in the fresh condition a pellucid aspect. 

 The cells vary much in size and in figure, some being spheroidal, others more pyri- 

 form. Each cell has a single unbranched nerve-fibre process extending obliquely 



Fig. 49. MAGNIFIED VIEW OF THE INNERMOST LAYER OF THE RETINA, SHOWING THE BUNDLES OF 



C'l'TIC NERVE FIBRES RADIATING FROM THE PAPILLA. (Merkel.) 



from its rounded inner extremity amongst the fibres of the preceding layer, with 

 one of which it is continuous. From the opposite end of the cell, which is fre- 

 quently imbedded in the substance of the succeeding layer, one, two, or more much 

 thicker protoplasmic processes extend outwards for a variable distance into that 

 stratum, and branch in its substance (fig. 50, v., vi., vn.). The branching occurs 

 at different levels for different cells, the smaller cells as a rule having the terminal 

 ramification of their protoplasmic processes nearer the ganglionic layer, the larger 

 ones nearer the inner nuclear layer. The arborisations are mostly flattened 

 conformably with the retinal strata, and in sections of retina produce the appearance 

 of coarse lines in the molecular stratum. The number of nerve-cells and con- 

 sequently the thickness of the ganglionic layer in the different regions of the retina 

 varies largely. Over the greater part of the retina they form a single stratum, 

 but in the neighbourhood of the yellow spot they are placed two or three deep. At 

 the spot itself (fig. 60, 2) they are very thickly set ; the cells are also smaller here. 

 Towards the ora serrata, on the other hand, there is but a single stratum, and that 

 frequently incomplete. 



