400 SPECIAL HISTOLOGY. 



easily enough. It is as well, however, to guide the cutting 

 scalpel by the handle of another held in the other hand, until 

 the edge of the former is brought immediately over the border 

 of the retina. When the nervous layers, which are very well 

 denned from each other, have been studied in sections of this 

 kind, which should be taken especially from the neighbourhood 

 of the macula lutea, as well as from other situations in the 

 transverse and longitudinal directions, and which when useful 

 necessarily exhibit only a few layers of the elements, they may 

 be carefully teased out or rendered more transparent by soda, 

 which last, however, is not generally of much use, since it 

 makes the elements pale. The hyaloid membrane is pos- 

 teriorly always very readily detached from the retina, together 

 with the vitreous body, and may be recognised in every eye, in 

 sections from the surface of that body, examined under the 

 microscope, and, in folds, occasionally by the naked eye. The 

 zonula Zinnii, on the other hand, in the recent eye, is always 

 so covered by detached pigment and the colourless epithelium of 

 the ciliary processes, and at its posterior border by the retina, 

 that it cannot well be recognised in that situation, and almost 

 only in its free, most anterior portion. In such preparations, also, 

 after the removal to the greatest possible extent of the adherent 

 parts by means of a hair pencil, pretty good views of it may be 

 obtained, particularly if, in addition to the viewing of the 

 external and internal surface of segments of the zonula 

 detached from the vitreous body, and of preparations made by 

 the teasing out of the structures, the borders of folds, espe- 

 cially of the inner surface, are also examined, which, with some 

 care, may be obtained to the whole extent of the zonula and of 

 its points of connexion with the retina. The zonula in con- 

 nexion with the hyaloid membrane, is very beautifully and 

 distinctly isolated from the retina and the cells of the ciliary 

 processes, in half-putrid eyes and in macerated preparations 

 of the vitreous body; and preparations of this kind are 

 especially adapted to show that the zonula is a part of the 

 hyaloid membrane, as well as the mode of origin and course of 

 its fibres. For the study of the zonular fibres I can also 

 particularly recommend chromic acid preparations, in which 

 they become quite opaque and glistening, almost like elastic 

 fibres. The capsule of the lens and its epithelium present no 



