DIRECTIONS FOB LABORATORY WORK 813 



ing the optic nerve.) Examine under water. Note: cornea, iris, crys- 

 talline lens, suspensory ligament (zonula ciliaris of Zinn) of4errs, an- 

 terior and posterior chambers with their content of aqueous humor; the 

 ciliary body with the ciliary folds and processes; the ora serrata; the 

 vitreous humor (body) ; the retina; the tunica choroidea; the sclera; the 

 lamina fusca and the lamina suprochoroidea between the separated por- 

 tions of the choroid and sclerotic coats ; the macula lutea with the f ovea 

 centralis; the optic papilla (disc) with the central depression (physio- 

 logic excavation); hyaloid canal; and the hyaloid membrane. Sketch 

 (376). Significance of the hyaloid canal (canal of Cloquet; canal of 

 Stilling) ? 



Eemove the lens. Note the difference in curvature of its anterior 

 and posterior surfaces. Eemove the anterior lens epithelium, and the 

 lens capsule. Remove the more superficial layer of lens fibers and free 

 the central non-nucleated lens 'nucleus'. Explain the arrangement of 

 the lens fibers, with relation to each other, the 'nucleus', and the poles 

 of the lens (lens 'stars'). Sketch (377). 



How is the lens held in place ? Describe the action of the lens. What 

 is a cataract of the eye? Difference between the anatomic axis of the 

 bulb and the visual axis? Embryonic origin of the several tunics and 

 humors of the bulbus oculi, and of the lens? What is the capsule of 

 Tenon? 



(B) MICROSCOPIC STUDY. 



(1) Study l.p. a stained horizontal section of the human eyeball (or 

 that of cat, dog or monkey). (The bulb should have been preserved in 

 Perenyi's fluid,* which softens the lens). Sketch (378). Note the 

 difference in curvature between the cornea and the posterior scleral seg- 

 ment of the bulbus oculi; also between the anterior and posterior sur- 

 faces of the lens. Identify the several chambers, angles and tunics of 

 the bulb, and the several laminae of each tunic. Note the disposition of 

 the nuclei in the lens. Enumerate and identify the intrinsic muscles of 

 the eye. Explain their nerve supply. Explain the action of the ciliary 

 body. Function of the aqueous chambers and the canal of Schlemm 

 (sinus venosus sclerse) ? Relation to glaucoma? Define astigmatism. 



(2) Study h.p. the sclero-corneal junction. Identify all of its con- 



* Perenyi 's 'fluid : 4 parts 10 per cent nitric acid 



3 parts alcohol (95%) 



3 parts 0.5 per cent chromic acid. 

 Fix 5 to 10 hours, and pass directly into 70% alcohol. 



