62 SECRETION. 



untary muscular fibres, and externally a few elastic fibres. 

 It is lined bj a single layer of irregularly polygonal cells, 

 from -g-gVo- to 12 1 00 of an inch in diameter. These cells con- 

 tain numerous brownish or yellowish pigmentary granules. 

 The tube forming the gland contains a clear fluid mixed 

 with a granular substance containing cells. 1 



In addition to the ceruminous glands of the ear, numer- 

 ous sebaceous follicles are found connected with the hair- 

 follicles here, as in other parts provided with hair. The 

 arrangement of the ordinary sebaceous glands and the ceru- 

 minous glands, which are situated in different planes in the 

 subcutaneous structure, is shown in Fig. 2. 



The Meibomian glands of the eyelids have essentially 

 the same structure as the ordinary sebaceous glands. Their 

 ducts, however, are longer, and the terminal follicles are ar- 

 ranged 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 upon the 

 inner edge, and occupying the entire width of the cartilages. 

 From twenty-five to thirty glands are found in the upper, 

 and from twenty to twenty-five in the lower lid. 



Each gland consists of a nearly straight excretory duct, 

 from -5-^-3- to ^-^ of an inch in diameter, communicating 

 laterally with numerous compound racemose acini, or col- 

 lections of follicles, measuring from T j ir to y^- of an inch. 

 From fifteen to twenty of these collections of follicles are 

 found on either side of the duct in glands of medium length. 2 

 Most of the excretory ducts are nearly straight, but some 

 are turned upon themselves near their upper extremity. 

 The general arrangement of these glands is shown in Fig. 3. 



1 The measurements of these tubes and cells are taken from Kolliker (op. 

 cit., 1860, p. 133). 



2 SAPPEY, Traite <? anatomic descriptive, Paris, 1852, tome ii., p. 598. 



