GLANDS OF MEIBOMIUS. 401 



a slight degree of putrefaction. The part immediately connected 

 with the cornea is extremely thin and delicate. 



This membrane closes the orbit of the eye, and completes 

 the cavity which contains the muscles, lachrymal glandf &c., 

 which are by this means precluded from contact with the exter- 

 nal air, 



The conjunctiva receives some very delicate nervous fibrils 

 from the branches of the fifth pair, called the lachrymal and 

 internal nasal. It contains, there is reason to believe, many 

 mucous cryptae or follicles, but from their minuteness, it is diffi- 

 cult to detect them. Stachow, however, asserts that with the 

 microscope he has seen them most distinctly, though in the pal- 

 pebral conjunctiva only. According to this observer they are 

 most numerous in the upper lid, and in the neighborhood of the 

 tarsal cartilages ; especially at their extremities. 



He found them in groups of 8, 12, or 15 together, and 

 sometimes 50 or 60. That portion of the ocular conjunctiva 

 which covers the sclerotica is sometimes called the tunica, 

 adnata. _ 



On the inside of each eyelid, apparently between the tunica 

 conjunctiva and the cartilages, are a number of lines running 

 inwards from the edge of the lid. These lines are of various 

 lengths, from one-fourth to near half an inch ; the longest are 

 in the middle of the upper lid. Some of them are straight ; 

 and others are serpentine : their color is a yellowish white. 

 There are generally more than thirty in the upper eyelid, and 

 more than twenty in the lower. They are called the glands 

 of Meibomius.* By pressure a sebaceous substance can be 

 forced out of them, in the form of fine threads, from orifices 

 on the edges of the eyelids. They are follicles into which the 

 sebaceous substance is secreted. This substance appears to 

 have a two-fold effect : it prevents the tears from running 

 over the eyelid, as any other unctious matter would do, and 



* Charles Etienne demonstrated the little sebaceous glands of the eyelids, 

 and Casserius caused them to be drawn and engraved a long time before Henry 

 Meibomius. The latter gave his name to them by a letter printed in Helmstadt 

 in 1666 ; in which they were accurately described. See Lassus. H. 



34* 



