DISEASES OF THE EYE. 277 



over it until the entire globe may be hidden from sight. This pro- 

 trusion of the cartilage so as to cover the eye may be induced in the 

 healthy eye by pressing the finger and thumb on the upper and lower 

 lids, so as to cause retraction of the eyeball into the socket. When 

 foreign bodies, such as sand, dust, and chaff, or other irritants, have 

 fallen on the eyeball or eyelids it is similarly projected to push them 

 off, their expulsion being further favored by a profuse flow of tears. 

 This is seen, to a lesser extent, in all painful inflammations of the 

 eye, and to a very marked degree in lockjaw, when the spasm of the 

 muscles of the eyeball draws the latter deeply into the orbit a;nd pro- 

 jects forward the masses of fat and the cartilage. The brutal prac- 

 tice of cutting off this apparatus whenever it is projected necessitates 

 this explanation, which it is hoped may save to many a faithful serv- 

 ant a most valuable appendage. That the cartilage and membrane 

 may become the seat of disease is undeniable, but so long as its edge 

 is thin and even and its surface smooth and regular the mere fact of 

 its projection over a portion or the whole of the eyeball is no evi- 

 dence of disease in its substance, nor any warrant for its removal. It 

 is usually but the evidence of the presence of some pain in another 

 part of the eye, which the suffering animal endeavors to assuage by 

 the use of this beneficent provision. For the diseases of the cartilage 

 itself, see " Encephaloid cancer." • 



LACRIMAL APPARATUS. 



This consists, first, of a gland for the secretion of the tears, and, 

 second, of a series of canals for the conveyance of the superfluoiis 

 tears into the cavity of th^ nose. 



The gland is situated above the outer part of the eyeball, and the 

 tears which have flowed over the eye and reached the inner angle are 

 there directed by a small, conical papilla (lacrimal caruncle) into 

 two minute orifices, and thence by two ducts (lacrimal) to a small 

 pouch (lacrimal sac) from which a canal leads through the bones 

 of the face into the nose. This opens in the lower part of the nose on 

 the floor of the passage and a little outside the line of union of the 

 skin which lines the false nostril with the mucous membrane of the 

 nose. In the ass and mule this opening is situated on the roof instead 

 of the floor of the nose, but still close to the external opening. 



EXAMINATION OF THE EYE. 



To avoid unnecessary repetition the following general directions are 

 given for the examination of the eye : The eye, and to a certain extent 

 the mucous membrane lining the eyelids, may be exposed to view 

 by gently parting the eyelids with the thumb and forefinger pressed 

 on the middle of the respective lids. The pressure, it is true, causes 



