750 SPECIAL HISTOLOGY. 



structures above described will be obtained, and it will excite surprise 

 that such numerous fibres pervading the entire retina should have been 

 hitherto overlooked. A wholly new investigation of the retina has com- 

 menced with what has been made known bj Muller and myself, but it 

 will still demand much time and pains before it can be conducted to any 

 certain results. Future inquirers should take up particularly the rela- 

 tions of the radiating and optic fibres in the eye, also the point whether 

 the latter subdivide in the retina, as is asserted by Hassall and Corti, 

 and lastly, whether the nerve-cells are directly connected with the 

 nerve-fibres (Corti) or not.* 



§ 228. The crystalline lens is a perfectly transparent body, in rela- 

 tion by its posterior surface with the vitreous humor, and laterally with 

 the termination of the hyaloid membrane, the zonula Zinnii ; and in 

 which are to be distinguished the lens, properly so termed, and its 

 capsule. 



The capsule of the lens consists of two elements — the ^jroper capsule 

 and the epithelium. The former is a perfectly structureless and trans- 

 parent, highly elastic membrane, enclosing the lens on all sides, as if 

 moulded to it, and parting it from the neighboring structures. If the 

 lens with its capsule be placed in water, the latter becomes considerably 

 distended by imbibition, whence it is apparent, that membranes of that 

 kind, notwithstanding their homogeneous structure, are yet very per- 

 meable, so that' the nutrition of the non-vascular lens is provided for 

 without difficulty, by means of materials penetrating from without. The 

 lenticular capsule, measuring in its anterior wall, 0'005-0-008 of a line, 

 and posteriorly to the attachment of the zonula Zimiii, where it is 

 abruptly thinned, not more than 0-002-0-003 of a line, may be readily 

 torn, punctured, or incised, whilst it oifers considerable resistance to a 

 blunt instrument. If an uninjured capsule be punctured, it contracts 



* [Profs. Kolliker and Muller {vid. Comiites. rend. torn, xxxvii., Sept. 1S53) have since 

 Ijeen able by further researches, to confirm their views on the structure of the retina. They 

 state also, that they have succeeded in tracing in the human retina the direct connection of 

 the nerve-fibres with the nerve-cells — a fact first noticed by Corti in the Ruminants, and 

 to which they attach extreme physiological importance. The radial fibres proceeding 

 from the "rods," Kolliker observed frequently to unite into fasciculi, which was not the case 

 in those derived from the " cones." At the yellow spot, he found the nerve-cells to consti- 

 tute a thick layer, formed of from 9 to 12 rows of cells; but both he and Milller deny most 

 strongly the presence of nerve-fibres in this situation, although their existence has been 

 (juite lately again positively afilrmed by Hannover (Zeitschrift fiir wiss. Zool. B. V. H. 1, 

 1853). 



The physiological conclusions which Kolliker and Miiller deduce from these more recent 

 anatomical observations are, in the main, the same as those above expressed. They seem, 

 however, less inclined to view the " rods" and " cones" as the only percipients of light, but 

 regard them more as conductors of the luminous impressions to the nerve-cells of the retina. 

 These they consider to form a true ganglion, capable of perceiving the light, the expansion 

 of the fibres of the optic nerve merely serving as a means of communication with the sen- 

 sorium. — DaC.j 



