562 



FILAMENTS OF MULLER. 



[sect. 226. 



Fig. 232. 



o*oo02'" to 0*0003'" in diameter ; the filaments being so delicate, 

 that the slightest mechanical injury suffices to break them off 

 close to their place of origin ; whence it has arisen, that observers 

 have hitherto known little beyond the proper rods, or when they 

 have observed filaments attached to the rods, have regarded them 

 as artificial products ; these filaments, too, as well as the points 

 of the rods, have been erroneously placed by all authors since 

 Hannover on the outer side of the bacillar layer. After a course 

 inwards of variable length, these fibres become connected with 

 one of the ordinary granules of the outer granular layer; the 

 filiform process of a rod attaching itself on the one side to a 

 granule, while a similar filament goes off from the opposite inner 

 side of it. In their further course, several of such filaments 

 frequently, if not always, unite to form a somewhat thicker fila- 

 ment (fig. 231, 3), being occasionally in- 

 terrupted by a granule ; and this filament, 

 like that of the cones, runs parallel to its 

 fellows through the intermediate granular 

 layer, which owes its radiated striation to 

 these elements; then it enters the inner 

 granular lamina?, with whose elements it 

 likewise becomes connected. Indeed, I 

 believe that I have found these filaments 

 to be chiefly, if not exclusively united 

 with the branched granules of this layer 

 (fig, 231, 2/, 30). 



The radiating fibre system of the retina 

 is by no means brought to an end by the 

 passage of the filaments from the cones 

 and rods into the outer and inner layers 

 of granules, for the filaments are continued 

 from hence through the entire innermost 

 layers of the retina, and ultimately ter- 

 minate at the membrana limitans in rather 

 a peculiar manner. In this second half 

 of their course, the fibres of Mi'dler re- 

 main completely isolated and separated 

 from one another, but become arranged, 

 towards the expansion of the optic nerve, 

 in a very definite manner, which is some- 

 what different in different regions of the 

 eye. At the bottom of the eye, and so 



A 



% 



IfSSS 



.9 



Perpendicular section of the 

 human retina, near the entrance 

 oftlie optic; magnified 350 times. 

 1. Bacillar layer; 2. outer gra- 

 nules ; 3. intermediate granular 

 layer ; 4. inner granules ; 5. 

 finely granular gray layer ; 6. 

 simple layer of nerve-cells; 7. 

 transverse section of the optic 

 bundles ; 8. Mtillerian fibres, 

 forming thin lamina? between the 

 optic bundles ; 9. termination of 

 the same at 10. the membrana 

 limitans. After a plate of the 

 retina in Ecker's hones Phus, 



