14 



VETEKINAEY OPHTHALMOLOGY. 



— ^undergoes change — audits action and function is now 

 the subject of much question. 



The question of inverted images, etc., will be more 

 fully dealt with in the lecture-room. Accommodation is 

 that faculty of the eye of adapting itself to distances of 

 varying degree, and is accomplished by the action of the 

 ciliary muscle upon the capsule of the lens, through the 

 zonule of Zinn. When accommo- 

 dated for near objects, the pupil 

 contracts ; when for more distant 

 objects, the obverse is the case. 

 These changes (contraction and 

 dilation) are reflex, and are 

 brought about by the action of 

 two sets of fibers (muscular) — the 

 sphincter, which are circular, sup- 

 plied by the 3d pair (motor-oculi) ; 

 and the dilator pupillse, which are 

 the radiating flbers,supplied almost 

 entirely by the trigeminus and the 

 cervical sympathetic. Now, sup- 

 pose we divide the 3d, what results ? 





Fig. 11. 

 P, pigment cell of the re- 



Mna connected with a Dilates of coursc : and why ? The 



rod. 11, Cone seated on ' ■' 



the membrana limitans sympathetic gcts in its work and is 

 in full possession of the field ; the 

 dilator fibers contract, and a wide open pupil is the 

 result. On the other hand, cause a solution of con- 

 tinuity in the sympathetic, and contraction is the re- 



