THE DISEASES OF CATTLE. 233 



posed of granules, from which spring the excretory ducts, and 

 thej, by inter-union, from a set of tubes which terminate on 

 the conjunctiva of the upper lid. The office of this gland is to 

 secrete the tears, which run into the ducts, and are then poured 

 on the conjunctiva. 



Canmcula Lachrymalis — At the inferior canthus of the. 

 eye, between the eyeball and eyelids, is seen a small black tu- 

 bercle, called the caruncula lachrymalis ; it is not a secretory 

 organ, but appears to be placed there for the mechanical pur- 

 pose of directing the tears into the puncta lachrymalis. 



Lachrymal Puncta and Conduits. — The puncta are two 

 small orifices, seen in the inner margins of the lids at the root 

 of the caruncle ; they are the openings of two canals found 

 within the substance of the lids, termed lachrymal conduits ; 

 they terminate in the lachrymal sac. 



Lachrymal Sac. — The lachrymal sac is a funnel shaped 

 membranous bag, lodged in close proximity with the lachrymal 

 foramen. This sac serves as a reservoir, into which the tears 

 flow from the lachrymal conduits ; the lachrymal sac terminates 

 in the ductus ad nasum. 



Ductus ad Nasum. — The office of this duct is to conveyN 

 away the tears as fast as they are collected within the lacliry- 

 mal sac ; the duct terminates at the inner and inferior part of 

 the nostril. It is formed by a prolongation of the membrane 

 which enters into the composition of the lachrymal sac. 



GLASS EYE.— (Guito 5ere/ja.) 



Glass eye — gvtta serena or amaurosis — is an abnormal 

 condition, which consists of dilatation of the pupil uninfluenced 

 by the ordinary stimuli, light and darkness, and occurs in con- 

 sequence of accidental or permanent paralysis of the optic 

 nerve and its ultimate expansion, the retina. 



Animals of an excita]>le nervous temperament often become 



the subjects of this affliction, as a temporary pathological con_ 



dition ; yet that form of amaurosis occurring among fat or 



plethoric subjects whose digestive organs are either deranged 



20* 



