THE LACHRYMAL APPARATUS. 



361 



The lachrymal gland resembles in shape and size a small almond and 

 consists of two fairly distinct parts, the superior orbital portion and the 

 inferior palpebral or accessory portion. The former occupies the fossa 

 lacrimalis in the frontal bone and is the larger portion, measuring 20 mm. in 



Alveoli 



Ducts 



Beginning of duct 



Fat-cells 



Fie. 410. Section of lachrymal gland, showing general arrangement of alveoli. X ao. 



length and 12 mm. in breadth. The lower portion of the gland, glandula 

 lacrimalis inferior, is smaller than the upper and separated from the latter 

 by a fascial expansion. 



The ducts from both portions of the gland are exceedingly fine, those 

 from the upper portion, from three to six in number, passing downwards 

 through the inferior portion. Some of the ducts from the lower gland join 

 those coming from above, while others run independently. They are lined 

 with a double layer of columnar epithelial cells. In all about a dozen ducts 

 open into the conjunctival sac along a line just in front of the fornix. In 

 structure the glands correspond to the tubo-alveolar type and resemble the 

 serous glands in their general character. The tubular alveoli contain cells of 

 two kinds columnar elements in which the stored secretion particles occupy 

 the inner half of the cells, and low elements whose cytoplasm may be almost 

 completely filled with secretory products. The alveoli of the lower portion 

 are separated by robust septa of connective tissue, which contain consider- 

 able lymphoid tissue. . 



Accessory lachrymal glands are found in both the upper and lower 

 fornices, from eight to twenty being present in the upper lid and from two 

 to four in the lower. They are very small and situated chiefly near the outer 

 angle of the palpebral fissure. 



The lachrymal passages begin by minute openings, the lachrymal 

 puncta, which are usually placed at the summit of the conical lachrymal 

 Papillce. The puncta lead into the lachrymal canaliculi, which at first are 

 vertically directed, then bend abruptly, take a nearly horizontal course, 

 and empty into the lachrymal sac. Each canaliculus is from 6-7 mm. in 

 length. Its lumen measures only .1 mm. in diameter at the punctum, 

 presents a diverticulum of I mm. at the bend, and continues with an 



