12S 



THE HOKJSE IN HEALTH AND DISEASE 



The eyelids are the most exposed parts. They are movable 

 !'ol(!s of skin on the margins of which the eyelashes are borne. 

 The third eyelid, haw, or nictitating membrane is an important 

 part of the eye of the hors(\ It consists of a plate of cartilage 

 covered liy a fold of the c(_)njunctiva. By frequently closing and 

 opening the eyelids the horse removes dust particles from the 

 cornea and keeps tlie e.ye in working ordei'. 



The conjunctiva is the mucous uiemln'ane .which hues the eye- 

 hds and is reflected on to tlie anterior part of the eyeball. It is 

 normallj^ of a bright pink color. 



Srkrn 



Opiic nert'c— 



OjiUc iiuinli'!" 

 Rt^tiobidhar JaV 



Rutus ocidi tnjt 



on of lovjuncliva 



\ Granulo iridis 



proub^es 



t2. — \'ortir;Ll section of cypbiill. The contour of the crystalline lens is 

 dotted. (Sisson, Anatomy of Domestic Animals.) 



Tlie lacrimal apparatus is made up of the lacrimal gland. 

 which secretes the tears; and the Incriinal duct, which carries 

 fh(> overflow of fluid to the nasal cavit}'. Tears assist in re- 

 moving the small particles, of dirt from the eyeball and keep it 

 moistened. 



The eyeball is composed of tlie s<\ginents of two spheres of 

 different sizi^s (Fig. 42). The anterior is the cornea; the pos- 

 terior, the sclera. The cornea is transi)arent, oval in outline, and 

 fits into the sclera like a crystal does into a watch. The sclera, 



