1864.] Mr. Hulke on the Minute Anatomy of the Retina. 139 



nule, the body contains an albuminous substance which in chromic acid pre- 

 parations retires as an opaque granular mass towards the outer end of the 

 body. The inner end of the body is prolonged inwards, in the form of a 

 pale, delicate fibre, which was sometimes followed through the layer of 

 inner granules into the granular layer. It does not appear to be struc- 

 turally connected with the inner granules. It is essentially distinct from 

 Miiller's radial fibres, and bears a considerable resemblance to the axis- 

 cylinder of nerve. That it ever proceeds from the outer granule associated 

 with the rod- or cone-body is doubtful, from the consideration (a) that where 

 the body is large, and the granule lies within at some distance from its 

 contour, the fibre is seen to leave the inner end of the body distinct from 

 the granule, and (/3) that the fibre appears to proceed from the outer 

 granule only where the body is small, as in the frog, and where the 

 granule does not lie within the body but is joined to this by a band. 

 Ritter's axial fibres are artificial products. 



6. The "outer granules" are large, circular, nucleated cells. Each 

 cell is so intimately associated with a rod- or cone-body that it forms an 

 integral part of it. 



7. The intergranular layer is a web of connective fibre. It contains 

 nuclei. 



8. The inner granules are roundish, in chromic acid preparations poly- 

 gonal cells. They differ from the outer granules by their higher refraction, 

 by the absence of a nucleus, and by receiving a deeper stain from carmine. 

 They lie in areolae of connective tissue derived from Miiller's radial fibres, 

 and from the intergranular and granular layer. They are more numerous 

 than the outer granules, and consequently than the rods and cones. 



9. The granular layer is a very close fibrous web derived in part from 

 Miiller's radial fibres, and from other fibres proceeding from the connective 

 frame of the layer of inner granules. It transmits (a) the radial fibres, 

 (/3) fibres proceeding radially outwards from the ganglion-cells and bundles 

 of optic nerve-fibres, and (y) fibres passing inwards from the rod- and cone- 

 bodies. 



10. The ganglion-cells communicate by axis-cylinder- like fibres with the 

 bundles of optic nerve-fibres, and send similar fibres outwards, which have 

 been traced some distance in the granular layer. 



11. In the frog and Spanish Gecko the author has a few times traced 

 fibres proceeding from the bundles of optic nerve-fibres for some distance 

 in a radial direction in the granular layer. 



12. Miiller's radial fibres arise by expanded roots at the outer surface 

 of the membrana limitans interna, pass radially through the layers, 

 contributing in their course to the granular layer, to the areolar frame of 

 the layer of inner granules, and end in the intergranular layer and at the 

 inner surface of the membrana limitans externa. They are a connective 

 and not a nervous tissue, and do not communicate between the basilary 

 element and ganglion-cells. 



M 2 



