THE EYE AND ITS APPENDAGES. 



371 



The nerves of the eyelids form the rich marginal plexus close 

 to the palpebral border ; the trunks taking part in the formation of 

 this plexus before their union give off branches to the orbicular 

 muscle and the skin, as well as additional twigs for the supply of the 

 conjunctiva. From the plexus itself fibres are distributed to the 

 hair-follicles of the cilia, the Meibomian glands, the tarsal conjunc- 

 tiva, and the tissues of the edge of the lid. The ultimate nervous 

 distribution includes the formation of subepithelial net-works of fine 

 non-medullated fibres, together with the special endings, the spherical 

 end-bulbs, occurring within the bulbar conjunctiva. 



THE LACHRYMAL APPARATUS. 



The lachrymal apparatus includes the lachrymal gland and the 

 system of canals carrying off the fluid secreted under usual con- 

 ditions. 



The lachrymal gland represents the serous racemose type, 

 closely resembling the true salivary glands in structure ; the organ 

 differs from the usual racemose gland in the independent course 

 and the number of its ducts, of which about a dozen are usually 

 present. It appears, therefore, more accurate to regard the lachry- 

 mal gland as a group of closely-placed small individual racemose 

 glands rather than as a single organ. 



The ducts of the lachrymal gland are lined by simple columnar 

 epithelium . The structure of the acini 

 and the relations of their groups corre- lG ' 



spend to those of the serous salivary 

 glands, the secreting cells possessing 

 similar spherical forms and granular pro- 

 toplasm. 



The blood-vessels of the lachrymal 

 gland form the usual capillary net-works 

 supplying the acini and their secreting 

 cells. 



. . , . . Section of human lachrymal gland: 



The nerves distributed to the glandu- a> acini) limited by basement-mem- 



lar tissue paSS between the acini and form Cranes (m) and lined by secreting cells 



() ; i. interacinous connective tissue. 



net-works beneath the basement-mem- 

 brane ; their ultimate relations to the secreting cells are uncertain. 



The lachrymal canals or canaliculi consist of three coats the 

 epithelium, the tunica propria, and the muscular tissue. The 

 epithelium is stratified squamous, and forms a layer about .12 

 mm. in thickness, in which the deepest cells are columnar and the 

 superficial greatly flattened. The tunica propria is composed of 

 bundles of fibrous tissue among which lie especially rich circularly- 

 disposed elastic net-works. Outside the tunica propria the lachry- 



