An American text-book of physiology . considered m connectionwith a description of the qualitative modifications of light The histological relation between the various layers of the retina is stillunder discussion. According to recent observations of Cajal,^ the connectionbetween the rods and cones on the oneside and the fibres of the optic nerveon the other is established in a man-ner which is represented diagram-matically in Figure 235. The pro-longations of the bipolar cells of theinternal nuclear layer E break up intofine fibres in the external molecular(or plexiform) layer C. Here they ar
An American text-book of physiology . considered m connectionwith a description of the qualitative modifications of light The histological relation between the various layers of the retina is stillunder discussion. According to recent observations of Cajal,^ the connectionbetween the rods and cones on the oneside and the fibres of the optic nerveon the other is established in a man-ner which is represented diagram-matically in Figure 235. The pro-longations of the bipolar cells of theinternal nuclear layer E break up intofine fibres in the external molecular(or plexiform) layer C. Here they arebrought into contact, though not intoanatomical continuity, with the termi-nal fibres of the rods and cones. Theinner prolongations of the same bipolarcells penetrate into the internal molec-ular (or plexiform) layer F, and therecome into contact with the dendritescoming from the layer of ganglion-cellsG. These cells are, in their turn, con-nected by their axis-cylinder processesAvith the fibres of the optic nerve. The Rods. Fig. representation of the xvWh the fibres Ol tne OpUC neive. -lh^ structure of the retina (Cajal): A, layer of rods AVltn tne noieb ui u ^ and cones- B external nuclearlayer; C. external bipolar cells which serve as connective ^°^^j;^i^;(^; plexiform) layer; e, internal un-links between the rods and the optic J-r:ay^er;^..int.^^^^^^^^^nerve-fibres are anatomically distin- ^^-^^^^.g^,;,.guishable (as indicated in the diagram) Die Retina der Wirbeltkiere, Wiesbaden, 1894. 776 AX AMERICAN TEXT-BOOK OF PHYSIOLOGY. from those wliicli perlonn the same tunetion lor the cones. Whatever be tlieprecise mode of connection between the rods and cones and the fibres of tlieoptic nerve, it is evident that each retinal element cannot be counectod withthe nerve-centres by a separate independent nerve-channel, since the retinacontains many millions of rods and cones, while the optic nerve has onlyabout 438,000 nerve-fibres, though of course such
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