286 SECRETION 



ordinary sebaceous glands. Their ducts, however, are longer, and the 

 terminal follicles are arranged in a peculiar manner by the sides of 

 the tubes along their entire length. These glands are situated partly 

 in the substance of the tarsal cartilages, between their posterior surfaces 

 and the conjunctival mucous membrane. They are placed at right 

 angles to the free border of the eyelids, opening on the inner edge and 

 occupying the entire width of the cartilages. Twenty-five to thirty 

 glands are found in the upper lid, and twenty to twenty-five, in the 

 lower lid. 



Each Meibomian gland consists of a nearly straight excretory duct, 

 s~ro to 2^0 f an * nc h (**3 to IO A 1 ) i n diameter, communicating laterally 

 with compound racemose acini, or collections of follicles, measuring 3^- 

 to yj^ of an inch (83 to 200 (JL). Fifteen or twenty of these collections 

 of follicles are found on either side of the duct in glands of medium 

 length. Most of the excretory ducts are nearly straight, but some are 

 turned upon themselves near their upper extremities. 



In general structure there is little if any difference between the 

 terminal follicles of the Meibomian glands and the follicles of the ordi- 

 nary sebaceous glands. They are lined with cells 2~gVo to TiVo" ^ an 

 inch (10 to 20 fi) in diameter. The cells contain fatty globules, but 

 these do not coalesce into large drops, such as are often seen in the 

 ordinary sebaceous cells. The follicles and ducts' are filled with the 

 whitish oleaginous matter which constitutes the Meibomian secretion, 

 or the sebum palpebrale. 



In addition to the Meibomian secretion, the edges of the palpebral 

 orifice receive a small quantity of secretion from ordinary sebaceous 

 glands of the compound racemose variety (ciliary glands), which are 

 appended in pairs to each of the follicles of the eyelashes, and from 

 sebaceous glands attached to the small hairs of the caruncula lachry- 

 malis. 



Ordinary Sebaceous Matter. Although it may be inferred, from 

 the great number of sebaceous glands opening on the cutaneous surface, 

 that the amount of sebaceous matter must be considerable, it has been 

 impossible to collect the normal secretion in quantity sufficient for ulti- 

 mate analysis. In some parts, as the skin of the nose, where the glands 

 are particularly abundant, a certain quantity of oily secretion is some- 

 times observed, giving to the surface a greasy appearance. This may 

 be collected in small quantity on a glass slide and examined micro- 

 scopically. It then presents a number of strongly refracting fatty 

 globules with a few epithelial cells. The cells, however, are not abun- 

 dant in the secretion as it is discharged upon the general surface; but 

 if the contents of the ducts and follicles are examined, cells will be 



