DISEASES OF THE EYE, ETC. 349 



margin, and the worm squeezed out with the aqueous humor. The 

 latter will be formed again. This operation will result disastrously 

 unless the greatest care and skill are employed. 



CORNEAL DERMATOMA (HAIRY TUMOR ON THE EYEBALL). 



In a few instances this has been seen as a congenital growth. The 

 tumor arises from the cornea or the sclerotic, covered by its respective 

 membrane, with a growth of hair upon its surface. These tumors may 

 be quite prominent or flattened, and are dark in color; the hair may 

 protrude between the eyelids, giving the animal the appearance of 

 having a double eyelid. 



Treatment. — A surgical operation becomes necessary for their re- 

 moval — one requiring a skilled operator. 



STRABISMUS (SQUINTING). 



This is a very rare affection among cattle. Strabismus may be 

 either single or double — affecting one eye or both. It is due to a 

 paralysis, or a weakening of one of the straight muscles of the eye- 

 ball. Generally it is a congenital defect, and the squinting is toward 

 the nose — strabismus convergens. It is best not to attempt to remedy 

 the defect, as the risk in an operation is greater than the chances of 

 success warrant. 



PTERYGIUM. 



This term is applied to a fleshy-colored membrane, triangular in 

 form, which most frequently grows from the inner angle of the eye 

 and extends over the cornea, thus interfering with vision. It may 

 grow from the outer angle, or even from the superior or inferior hem- 

 isphere of the eyeball. The figure is invariably that of a triangle, 

 with its base on the white of the eye, and its apex more or less 

 advanced over the cornea toward its center. 



The distinguishing characteristics are the constancy of the triangu- 

 lar form, and the facility with which the whole of it may be taken 

 hold of with a pair of forceps and raised into a fold on the cornea. 

 Every other kind of excrescence attached to this membrane continues 

 firmly adherent to it, and can not be folded and raised from the sur- 

 face of the cornea in any manner whatever. 



Treatment. — Raise the fold and dissect it away from all points of 

 attachment. 



TRICHIASIS (INVERSION OP THE EYELASHES). 



In the simplest form the eyelashes bend inwardly, touching the 

 eyeball, causing irritation and simple conjunctivitis. It may be also 

 associated with entropion. 



Treatment. — The offending eyelashes should be cut off or pulled 

 out. In cases where the natural growth of the eyelashes is directed 

 inward an operation similar to that for entropion becomes necessary. 



