THE EYE. 765 



is posteriorly always very readily detached from the retina, together 

 with the vitreous body, and may be recognized 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 colorless epithelium of the ciliary processes, and at its posterior 

 border by the retina, that it cannot well be recognized in that situation, 

 and almost only in its free, most anterior portion. In such prepara- 

 tions, 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, especially 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 connection with the retina. 

 The zonula, in . connection with the hyaloid membrane, is very beauti- 

 fully 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 difficul- 

 ties. The tubes of the lens, when fresh, are very transparent, but in 

 dilute chromic acid they are rendered quite distinct. Sections of the 

 lens may be easily procured from preparations made in alcohol, or 

 chromic acid, or from dried and hardened preparations, which may be 

 rendered transparent again by means of acetic acid. The accessory 

 organs of the eyes require no particular remark, unless, with respect 

 to the Meibomian glands, it may be stated, that they are best seen in 

 tarsi which have been cleanly dissected and treated with acetic acid and 

 alkalies, and in longitudinal and transverse sections of similar prepara- 

 tions, dried. 



Literature. THE "EYE" AS A WHOLE: Valentin, in his " Report.," 

 1836 and 1837, and " Handw. d. Physiol.," I. p. 748 ; S. Pappenheim, 

 " Gewebelehre d. Auges," Berlin, 1842 ; E. Briicke, " Anat. Beschreib, 

 d. menschlichen Augapfels," Berlin, 1847; W. Bowman, "Lectures on 

 the parts concerned in the operations on the eye and on the structure of 

 the Retina and Vitreous Humor," London, 1849 ; A. Hannover, " Bidrag 

 til Ojets Anatomic, Physiologic og Pathologic," Copenhagen, 1850. SCLE- 

 ROTICA: M. Erdl, "Disquisit. anat. de oculo," I. " De m. sclerotic^," 



