14 



PRACTICAL PHYSIOLOGY 



OfM 



ciliary processes. Examine these processes. Note that the iris is 

 continued forward from them to the edge of the pupil. 



Shell the crystalline lens out 

 of its capsule. Study its shape 

 and note its elastic character. Ob- 

 serve the aqueous humour in front 

 of the lens and behind the cornea, 

 filling the anterior chamber. 



Now make a section through the 

 cornea and sclerotic at right angles 

 to the last cut. Study and draw 

 the corneo-sclerotic junction with 

 the adjacent tissues. 



Examine sections of this part of 

 the eye with the microscope and 

 identify and study the radiating 

 fibres of the ciliary muscle, noting 

 the origin and insertion, and the 

 two sets of muscular fibres in the iris. 

 In the posterior segment of the 

 eye note the entrance of the optic 

 nerve, and observe the thin mem- 

 brane-like retina spread over the 

 choroid. Note the iridescence in 

 front of the choroid in the eye of 

 the ox. Observe the blood ves- 

 sels entering in the optic nerve 

 and spreading over the front of 

 the retina. (In the eye of the 

 ox there is no special develop- 

 ment of a macula lutea in the 

 posterior optic axis.) Make 

 drawings of the various struc- 

 tures seen. 



Study the model of the human 

 eye provided. 



II. Examination of the Eye in 

 Life. Ophthalmoscope 



Make a model eye by unscrew- 

 ing the lower lens of a micro- 

 scope eyepiece and placing inside 

 it a piece of paper with some 

 mark upon it . Look through the 

 upper lens, and observe that the 

 chamber is dark and the paper 

 is not distinctly seen. 



FIG. 1. Horizontal median 

 section through the eye. 



Opt.N., Optic nerve. Sd., Sclerotic. 

 Cor., Cornea. Chor., Choroid. CO/., 

 Ciliary process with ciliary muscle. 

 S.L., Suspensory ligament. D.P., 

 Dilator pupillae. Hph.P., Sphincter 

 pupillse. L., Lens. 

 (From N5cl Paton's Essentials.) 



FIG. 2. Various forms of ophthal- 

 moscope. 



(a) Direct Method. In the optical room fix the model eye in 

 the holder, and bring the electric light beside it so that it does not 



