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THE SKIN. 153
The number and size of these glands connected with each follicle do
not depend upon the calibre of the hair, for some of the finest hairs
found upon the surface of the body have as many as six sebaceous
glands emptying into their follicles. Occasionally the gland has its
outlet upon the surface of the skin.
The largest of this variety of glands are found in connection with
the eyelashes, within the eyelid, and have received the name of Mei-
bomian glands. Sebaceous or cystic tumors, which sometimes appear on
the external surface of the head and in the eyelids, are caused by the
clogging of the orifices of these glands while active secretion goes on
within. The secretion of these glands on the face often becomes inspis-
sated, especially in the region of the alse nasi.
Sebaceous glands diifer in shape, though their general outline is pyri-
form, the duct of the gland corresponding to the stem of the pear.
In structure they are lobular (Fig. 78), each lobule consisting of a
Fig. 78.

Sebaceous Gland of the btcoud Class, from the ate nasi.
cluster of spherical secreting saccules. The secretion of each saccule is
collected into the principal duct of the lobule, and passes into the main
duct of the gland, which usually has its outlet a little below the mouth
of the hair-follicle.