CHAPTEE III. 



OPTIC NERVES ANATOMY OF THE EYE. 



General considerations Physiological anatomy of the optic nerves General 

 properties of the optic nerves Physiological anatomy of the eyeball Di- 

 ameters of the eyeball Sclerotic coat Cornea Membrane of Descemet, 

 or of Demours Ligamentum iridis pectinatum Choroid coat Uvea 

 Ciliary processes Ciliary muscle Iris Canal of Schlemm, or circular 

 venous sinus Pupillary membrane Retina Jacob's membrane Crystal- 

 line lens Suspensory ligament of the lens Zone of Zinn Aqueous humor 

 Chambers of the eye Vitreous humor Summary of the anatomy of the 

 globe. 



VISION, one of the most important and delicate of the 

 special senses, involves, not only the impressions conveyed by 

 the optic nerves to the brain, but the action of accessory 

 parts, the structure of which is exceedingly complex. The 

 integrity of these parts is absolutely essential to perfect 

 vision ; and they are liable to be injured by disease or other- 

 wise in a great variety of ways. At the present day, the 

 treatment of diseases of the eye is, to a great extent, con- 

 fined to those who have made its physiology and pathology a 

 special study ; and, thanks to the labors of Helmholtz, Don- 

 ders, Yon Graef e, and a host of other writers, ophthalmology 

 ranks among the most advanced of the subdivisions of medi- 

 cal science, with a literature exceedingly full and exact. 



Probably there is no department of medicine, in which 

 the principle, that the true basis of pathology is a thorough 

 knowledge of anatomy and physiology, is more completely 

 carried out than in ophthalmology. In many of the elaborate 

 works on diseases of the eye, the anatomy of the parts and 

 the physiology of vision are treated of very minutely. To 



