910 THE ORGANS OF SENSE. 



oval form, about the size and shape of an almond. Its upper convex surface is in 

 contact with the periosteum of the orbit, to which it is connected by a few fibrous 

 bands. Its under concave surface rests upon the convexity of the eyeball and 

 upon the Superior and External recti muscles. Its vessels and nerves enter its 

 posterior border, whilst its anterior margin is closely adherent to the back part of 

 the upper eyelid, where it is covered to a slight extent by the reflection of the con- 

 junctiva. The fore part of the gland is separated from the rest by a fibrous septum ; 

 hence it is sometimes described as a separate lobe, called the palpebral portion of 

 the gland (accessory gland of Rosenmuller). Its ducts, about seven in number, 

 run obliquely beneath the mucous membrane for a short distance, and, separating 

 from each other, open by a series of minute orifices on the upper and outer half 



FIG. 538. The lachrymal apparatus. Right side. 



of the conjunctiva near its reflection on to the globe. These orifices are arranged 

 in a row, so as to disperse the secretion over the surface of the membrane. 



Structure of the Lachrymal Grland. In structure and general appearance the 

 lachrymal resembles the serous salivary glands (page 946). In the recent state the 

 cells are so crowded with granules that their limits can hardly be defined. They 

 contain an oval nucleus, and the cell-protoplasm is finely fibrillated. 



The lachrymal canals commence at the minute orifices, puncta lachrymalia, 

 on the summit of a small conical elevation, the lachrymal papilla, seen on the 

 margin of the lids at the oute*r extremity of the lacus lachrymalis. The superior 

 canal, the smaller and shorter of the two, at first ascends, and then bends at an 

 acute angle, and passes inward and downward to the lachrymal sac. The 

 inferior canal at first descends, and then, abruptly changing its course, passes 

 almost horizontally inward to the lachrymal sac. These canals are dense and 

 elastic in structure and somewhat dilated at their angle. The mucous membrane 

 is covered with scaly epithelium. 



The lachrymal sac is the upper dilated extremity of the nasal duct, and is 

 lodged in a deep groove formed by the lachrymal bone and nasal process of the 

 superior maxillary. It is oval in form, its upper extremity being closed in and 

 rounded, whilst below it is continued into the nasal duct. It is covered by a fibrous 

 expansion derived from the tendo oculi. and on the inner side it is crossed by the 

 Tensor tarsi muscle (Horner's muscle, page 395), which is attached to the ridge 

 on the lachrymal bone. 



Structure. It consists of a fibrous elastic coat, lined internally by mucous 

 membrane, the latter being continuous, through the lachrymal canals, with the 

 mucous lining of the conjunctiva, and, through the nasal duct, with the pituitary 

 membrane of the nose. 



