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AREOLAE TISSUE, TEXDO^S, AXD MUSCLES. 203

tissue, at which point the duct divides into several smaller ones, each
of which enlarges innuediately after bifurcation and forms a separate
infundibulum ; the tubes again narrow and make several irregular turns
or convolutions, and have acsecal termination. It is these small twisted
tubes that form the secreting part of the gland. The epithelium lining
the glands varies in their different portions : the funnel-shaped moutii
has in man a stratified or pavement epithelium.
The duct proper is lined by a single layer of long, narrow, columnar
cells with intracellular and intranuclear network, giving a distinct long-
itudinal striation and slightly granular appearance to the cell. The
calibre of the duct is of considerable width.
The infundibular portion is lined with more or less flattened epithelial
cells, which gives comparatively a wide lumen to this portion of the
gland. The epithelial cells lining the convoluted portion of the small
tubes are columnar and very slightly granular, with a round or oval
nucleus situated near the outer end of the cell. The cell and nucleus
are made up of a network of fibrils, forming rather large meshes when
the gland is fully developed.
When the gland is active the cell contains drops of mucin ; but when
it is inactive the cells are shorter, and become very granular and some-
what opaque ; the lumen of this part of the gland is large.
The epithelium of these glands rests upon the basement-membrane,
and is made up of connective-tissue cells which are more branched, some
of the branches penetrating the septa between the intercellular cement
which holds them together.
Sometimes in the convoluted portion of the glands several embryonal
cells are found ; these are located between the columnar epithelium and
the cells forming the basement-membrane or connective tissue of the
tubes.
These compound tubular glands sometimes assume a saccular form,
thus giving us the names of tubular, saccular, or racemose glands.
Sacculo-tubular glands are those which are intermediate in form
between saccular and tubular. The saccules or acini have a tubular
form.
The racemose glands, so called from their resemblance to bunches of
grapes, are modifications of the compound tubular glands, containing a
multitude of saccules having a rounded, pyriform, or thimljle shape ;
they are arranged in clusters, forming lobules and open into the extremi-
ties of the branched tubes; these tubes form ducts which join other sac-
cular ducts, forming larger branches of the clusters or lobules ; the
lobular branches join together and form the main duct or ducts of the
whole gland, which empties its fluid upon the mucous membrane. The
size of the gland usually depends upon the number of lobules or clusters
and the number of saccules in a lobule ; thus there are the small race-
mose glands, as those of the roof of the mouth, and others of large size,
like the parotid.
Mucus.—The fluid that is secreted by these glands is viscid, lubrie,
and transparent. Examined under the microscope, it is found to con-
tain epithelial cells, also round cells or mucous corpuscles. They so
closely resemble the white or pale blood-corpuscles that they are con-