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208 ANATOMY.

the ear, is the largest of the salivary glands. Its size varies consider-
ably in difterent people, the average ^veight being one ounce. It is a
compound tubular racemose salivary gland.
Situation.— The Parotid Space is bounded in great part by a bony
framework, although the gland is not confined by the lines of the bony
structures. Anteriorly, it is bounded by the ramus of the inferior max-
illary bone posteriorly, by the mastoid and styloid processes and the
;
tympanic portion of the temporal bone ; its superior boundary is
formed by the convergence of the above structures ; belo\v, the boundary
is formed by an imaginary line drawn from the angle of the jaw to the
sterno-cleido-mastoid muscle. Between the mastoid and styloid pro-
cesses the gland comes in juxtaposition with the transverse processes
of the ujiper cervical vertebra, especially the atlas. Upon examination
of an articulated skeleton it will be observed that by depressing the head
upon the chest this bony space will be decreased by the jaw coming
closer to the vertebrae, while in the movement of raising or extending
the head it is enlarged. By protruding the lower jaw until the inferior
teeth articulate outside the superior, the space also is enlarged. If the
jaw is depressed the space becomes compressed below, while above it is
increased by the slipping forward of the condyle.
The parotid gland has a very irregular shape ; its superficial surface
is convex and lobulated and in close relation with its external fascia.
The anterior surface is divided by a perpendicular groove into an exter-
nal and an internal portion, the external of which extends forward to a
varied extent over the masseter muscle. It is from this anterior portion
that the parotid duct (duct of Steno) is given off; the internal portion
passes forward on the inside of the ramus between the pterygoid muscles.
The deep portion of the gland passes far inward toward the base of
the skull, vertebrae, and pharynx ; the upper portion passes into and
occupies the posterior part of the glenoid fossa ; the posterior and lower
portion rests upon the styloid process and its muscles, the sterno-cleido-
mastoid and digastric.
The Glandula Soda Parotidis, or Accessory Parotid, is a small sepa-
rate lobe, not always present, situated at the anterior external border,
below the zygomatic arch and upon the masseter muscle. The duct of
this lobe enters the parotid duct, where it crosses the masseter nuiscle.
The Parotid Duct, or Duct of Steno (or Steno's canal), is about tw^o
and a half inches in length, its diameter varying at dilferent portions,
its orifice being the narrowest part, only permitting the entrance of a
small probe. Where it pierces the buccinator muscle it is as large as
a crowquill, and at the position where it passes over the masseter mus-
cle it is from one-twelfth to one-eighth of an inch in diameter. The
duct commences at the anterior portion of the gland, leads over the
masseter muscle about one finger's breadth below the zygomatic arch, and
passes forward beneath an imaginary line drawn from the lower mar-
gin of the concha of the ear to a point midway between the ala of the
nose and the red margin of the upper lip, the transverse facial artery
lying above it. At the anterior border of the masseter muscle the duct
makes a short curve, almost at a right angle, inward ; thence it passes
through the cushion of fat and the buccinator muscle
; continuino-