262 BUREAU OF ANIMAL INDUSTRY. 



The two lachrymal openings, situated at the inner angle of the eye, 

 ma}' fail to admit the tears by reason of their.deviation outward in 

 connection with eversion of the lower lid, or b}'- reason of their con- 

 striction in inflammation of the mucous membrane. The lachrymal 

 sac, into which the lachrymal ducts open, may fail to discharge its 

 contents bj- reason of constriction or closure of the duct leading to the 

 nose, and it then forms a rounded swelling beneath the inner angle 

 of the eye. The duct leading from the sac to the nose maj^ be com- 

 pressed or obliterated by fractures of the bones of the face, and in 

 disease of these bones (osteosarcoma, so-called osteoporosis, diseased 

 teeth, glanders of the nasal sinuses, abscess of the same cavities). 



The narrowed or obstructed ducts may be made pervious by a fine 

 silver probe passed down to the lachrymal sac, and any existing inflam- 

 mation of the passages may be counteracted by the use of steaming 

 mashes of wheat bran, by fomentations or wet cloths over the face, 

 and even by the use of astringent eyewashes and the injection of 

 similar liquids into the lachrymal canal from its nasal opening. The 

 ordinary eyewash maj' be used for this purpose, or it may be injected 

 after dilution to half its strength. The fractures and diseases of the 

 bones and teeth must be treated according to their special demands 

 when, if the canal is still left pervious, it may be again rendered useful. 



EXTERNAL OPHTHALMIA, OK CONJUNXTIVITIS. 



In inflammation of the outer parts of the eyeball the exposed vas- 

 cular and sensitive mucous membrane (conjunctiva) which covers the 

 ball, the eyelids, the haw, and the lachrym.al apparatus, is usually the 

 most deeply involved, yet adjacent parts are more or less implicated, 

 and when disease is concentrated on these contiguous parts it consti- 

 tutes a phase of external ophthalmia which demands a special notice. 

 These have accordingly been already treated of. 



Causes. — The causes of external ophthalmia are mainly those that 

 act locally— blows with whips, clubs, and twigs, the presence of for- 

 eign bodies like hay seed, chaff, dust, lime, sand, snufl", pollen of plants;, 

 flics attracted by the brilliancy of the ej* e, wounds of the bridle, the 

 migration of the scabies (mange) insect into the ej^e, smoke, ammonia 

 rising from the excretions, irritant emanations from drying marshes, 

 etc. Iload dust containing infecting microbes is a common factor. A 

 very dry air is alleged to act injuriously by drying the eye as well as 

 by favoring the production of irritant dust; and the undue exposure 

 to bright sunshine through a window in front of the stall, or to the 

 reflection from snow or water, is undoubtedl}^ injurious. The unpro- 

 tected exposure of the eyes to sunshine through the use of a very 

 short overdraw check is to be condemned, and the keeping of the horse 

 in a very dark stall from which it is habitually led into the glare of 

 full sunlight, intensified by reflection from snow or white limestone 



