60 CLINICAL DIAGNOSTICS. 



organ must be free from local irritation. Severe ex- 

 ercise, and high atmospheric temperature cause a 

 healthy mucous membrane to appear very red from 

 physiological congestion ; local inflammation also produces 

 congestions. 



A careful comparison of both eyes will enable us to deter- 

 mine the presence of local inflammation. In healthy animals 

 the color of the conjunctiva is pale-roseate; in the ox paler 

 than in other animals. A few blood vessels are always visible. 

 In the conjunctiva, the boundary between normal and diseased 

 conditions is not sharply drawn, hence practice alone makes 

 one capable of giving a reliable judgment. 



I. Discharge from eyelids. Although mostly due to 

 local diseases, some of the infectious diseases have dis- 

 charges from the eyelids constantly present. The dis- 

 charge is either bilateral (from both sides] or un- 

 ilateral (from one side only). Bilateral discharges are 

 seen in: malignant head catarrh (with keratitis), Rin- 

 derpest (no keratitis present), dog distemper, fowl 

 cholera, influenza. (Swelling shuts off the tear ducts, 

 strangles). Unilateral discharges occur: in continued 

 chronic nasal catarrh, a symptom of glanders, chronic nasal 

 or sinus catarrh. In all animals showing unilateral dis- 

 charge from the eyelids, especially when the discharge is 

 copious, a careful examination for foreign bodies should be 

 made]. 



II. Color. The color of the conjunctiva is due to the 

 quantity of blood circulating in the blood vessels of the organ 

 and the amount of hemoglobin contained in the blood cor- 

 puscles. 



1. A pale, anemic color shows that the animal is either 

 deficient in blood or that the blood does not contain its nor- 

 mal quota of red corpuscles. The color varies from reddish- 

 white to greyish-white or white. 



Paleness occurs suddenly : 



Following great loss of blood, internal hemorrhages (liver, 

 heart, large blood vessels, etc). 



