LACHRYMAL APPARATUS. 143 



teum by its upper surface, and is moulded below to the con- 

 vexity of the globe. Its anterior portion is separated from 

 the rest by a well-marked groove, is comparatively thin, and 

 adheres to the upper lid. It presents from six to eight, usu- 

 ally seven, ducts, which form a row of openings into the con- 

 junctival fold. Five or six of these orifices are situated above 

 the outer canthus and two or three open below. In its mi- 

 nute structure, this gland presents no points of special physi- 

 ological interest as distinguished from the ordinary racemose 

 glands. It receives nervous filaments from the fifth cranial 

 nerve and the sympathetic. 



The apparatus by which the excess of tears is conducted 

 into the nose begins by two little points, situated on the mar- 

 gin of the upper and the lower lid, near the inner canthus, 

 called the puncta lacrymalia, which present each a minute 

 orifice. These points lead respectively into the upper and 

 the lower lachrymal canals, w T hich together surround the ca- 

 runcula lacrymalis. At the inner angle, just beyond the ca- 

 runcula, the two canals join, to empty into the lachrymal sac, 

 which is the dilated upper extremity of the nasal duct. The 

 duct is about half an inch in length, and empties into the 

 inferior meatus of the nose, taking a direction nearly vertical, 

 inclined slightly outward and backward. This portion of 

 the lachrymal apparatus is fibrous and is lined by a reddish 

 mucous membrane, which presents several well-marked folds. 

 Near the puncta, are two folds, one for each lachrymal canal. 

 Another pair of folds exists near the horizontal portions of 

 the canals. At the opening of the duct into the nose, is an 

 overhanging fold of the nasal mucous membrane. These 

 folds are supposed to prevent the reflux of fluid from the 

 lachrymal canals and the entrance of air from the nose. The 

 mucous membrane of the lachrymal canals is covered by a 

 flattened epithelium, like that of the conjunctiva. The lach- 

 rymal sac and duct are lined by a continuation of the ciliated 

 epithelium of the nose. The disposition of the apparatus 

 just described is shown in Fig. 9. 

 140 



