SECT. 



226.] 



FILAMENTS OF MUIJ.ER. 



563 



far as tlio optic bundles have only narrow fissure-shaped spaces 

 between them, the fibres of Mutter collect to form thin laminae, 

 which vary in extent according to the size of the meshes of the 

 nervous plexus ; in this form they arc continued through the whole 

 layer of the optic nerve-fibres, as may be seen both on transverse 

 section through the optic expansion, or when viewed from the sur- 

 face. Transverse sections (fig. 232) exhibit the flat bundles, some 

 of them very thick, of the optic fibres as finely dotted columnar 

 masses; while between them, forming coarser fibrous bundles, are 

 seen the lamellre of the fibres of Midler in profile; in the meshes 

 of the nervous plexus, the terminations of these fibres are seen in 

 the form of beautiful narrow rows of dark streaks and points, which 

 in animals often appear directed in a regular penniform manner 

 towards both sides. Further forwards, where the meshes of the 

 nervous plexus become wider, the laminae of the fibres of Mailer 

 increase more and more in thickness, and at last, at the most an- 

 terior part of the retina, they pass pretty close and parallel to each 

 other towards the surface without presenting any other special ar- 

 rangement ; and they now appear on the surface as an almost con- 

 tinuous layer of dark points, this layer being interrupted only at the 

 places where nervous bundles and large nerve-cells are situated. 



The inner terminations of the filaments of 

 Miiller pass through the layer of optic nerve- 

 fibres, and reach the membrana limitans; but 

 their arrangement here is somewhat difficult to 

 ascertain, on account of their great delicacy and 

 the ease with which they are injured. From all that 

 I have seen, I think I am warranted in assuming, 

 that the triangular truncated swellings, observed 

 by II. Midler and previously by myself, and not 

 the divisions and ramifications which also fre- 

 quently occur, represent the true condition of 

 these fibres at their terminations. These ter- 

 minations, when a fold or a perpendicular section 

 of a fresh retina is examined, appear as a clear 

 border, 0-002'" to 0-003'" broad, between the 

 membrana limitans and the expansion of the 

 optic nerve ; and this appearance has given rise, 

 as I now find, to a belief in the presence of an 

 epithelium in this situation. The clear globules, 

 indeed, which Bowman {Led., fig. 15) describes, 



Fig. 233. 



are nothing else than the inner terminations of 



o o 2 



From the human 

 retina ; magnified 300 

 times, a. A large 

 nerve-cell ; b. process 

 from the same di- 

 rected outwards, to- 

 wards c. an internal 

 nucleus (cell with a 

 nucleus) ; d. filament 

 of Miitter, proceeding 

 from the bacillar layer 

 to this granule; e. 

 second process of the 

 nerve-cell, which is 

 undoubtedly conti- 

 nued into one of the 

 fibres of the optic 

 nerve. 



