302 THE DOG IN DISEASE. 



period to treatment, a careful examination of the ear 

 should be made with a speculum in a bright light. If a 

 polypus is discovered and it can be reached with a for- 

 ceps, snare, etc., its immediate removal is indicated, the 

 base being cauterized with nitrate of silver or carbolic 

 acid if possible, and the wdiole finally destroyed by re- 

 peated astringent applications (powders). 



DISEASES OF THE EYE. 



The visual apparatus consists of a series of refracting 

 bodies which bring rays of light emanating from an object 

 to a focus on the expansion of the optic nerve {retma) in 

 the form of a clearly defined image, which so influences 

 the nerve of vision that certain parts of the brain are af- 

 fected, and '' seeing " or " vision " results. 



The principal refracting body is the crystalline lens. 

 The essential apparatus {crystalline lens and retina), so far 

 as the globe of the eye is concerned, is protected by a firm 

 whitish outer tunic, lined within by a vascular (blood- 

 supplying) covering supporting the retinal expansion of 

 the nerve of vision. 



The main refracting body is supported in position by 

 a ligament {suspensory ligament), the foldings {ciliary 

 processes) of the vascular, pigmented coat {choroid), and 

 the vitreous humor. 



Light is admitted through the clear outer cornea, 

 which is set into the rest of the globe as a watch-glass into 

 its case. At the junction of this cornea and the firm outer 

 coat {sclerotic) hangs, in front of the lens, a colored (pig- 

 mented) circular muscular curtain {iris) with the power to 

 vary in size under the stimulus of light reflex/h^ so that 



