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 whole 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 (retina) 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 reflexly, so that 



