404 DIGESTIVE SYSTEM OF THE HORSE 
THE SALIVARY GLANDS 
This term is usually restricted to the three pairs of large glands situated on the 
sides of the face and the adjacent part of the neck—the parotid, mandibular, and 
sublingual. Their ducts open into the mouth. 
The parotid gland (Glandula parotis) (Fig. 560)—so named from its proximity 
to the ear—is the largest of the salivary glands in the horse. It is situated chiefly 
in the space between the ramus of the mandible and the wing of the atlas. It is 
somewhat triangular in shape, the apex partially embracing the base of the external 
Its length is about eight to ten inches (ca. 20 to 25 em.), and its average thick- 
ear. 
Its average weight is about seven ounces (ca. 
ness nearly an inch (ca. 2 em.). 
200 to 225 ¢g.). It presents for description two surfaces, two borders, a base, and 
an apex. The lateral (or superficial) surface is covered by the parotid fascia and 
the cutaneus and parotido-auricularis muscles. It is crossed obliquely by the jugular 
vein, which is largely embedded in the gland. It is also related to the great auricular 
vein, the cervical branch of the facial nerve, and branches of the second cervical 
nerve. The medial (or deep) surface is very uneven, and has numerous important 
relations. Some of these are: the guttural pouch and the great cornu of the 
hyoid bone; the masseter, occipito-mandibularis, digastricus, and occipito-hyoideus 
muscles; the tendons of the brachio-cephalicus and sterno-cephalicus (which 
separate the parotid from the underlying mandibular gland); the external carotid 
artery and some of its branches; the facial nerve; the pharyngeal lymph glands. 
The anterior or facial border is closely attached to the ramus of the mandible and 
the masseter muscle; it overlaps the latter to a varying extent.! The posterior 
or cervical border is concave, and is loosely attached to the underlying muscles. 
The base or ventral border is related to the external maxillary vein. The apex 
is attached to the base of the external ear, which it partially embraces. The gland 
has a yellowish-gray color and is distinctly lobulated. It is inclosed in a capsule 
formed by the fascia. The parotid duct (Ductus parotideus)? is formed at the 
ventral part of the gland, near the facial edge, by the union of three or four radicles. 
It leaves the gland about an inch (ca. 2 to 3 cm.) above the external maxillary 
vein, crosses the tendon of the sterno-cephalicus, and gains the medial face of the 
pterygoideus medialis. It then runs forward in the mandibular space below the 
external maxillary vein and winds around the ventral border of the mandible be- 
hind the vein, passes upward between the vein and the masseter muscle for about 
two inches (ca. 5 em.), turns forward underneath the facial vessels, and perforates 
the cheek obliquely opposite the third upper cheek tooth. Before piercing the 
cheek it is somewhat dilated, but its termination is small, and is surrounded by a 
circular mucous fold (Papilla salivalis). The gland belongs to the compound 
alveolar glands of the serous type. 
Blood-supply.— Branches of the carotid and maxillary arteries. 
Nerve-supply.—Trigeminal, facial, and sympathetic nerves. 
The mandibular or submaxillary gland (Glandula mandibularis s. submax- 
illaris)® is much smaller than the parotid. It is long, narrow, and curved, the 
dorsal edge being concave. It extends from the fossa atlantis to the body of the 
hyoid bone, so that it is covered partly by the parotid gland, partly by the lower 
jaw (Fig. 646). Its length is eight to ten inches (ca. 20 to 25 em.), its width an inch 
2.5 to 3 em.), and its thickness about half an inch (ca. 
to an inch and a half (ca. 
It is often 
lem.). It weighs about one and a half to two ounces (ca. 45 to 60 g.). 
1Tn some cases there is a well-marked triangular facial process, which covers the temporo- 
mandibular joint, the facial nerve, and the transverse facial vessels. 
2 Formerly known as Stenson’s or Steno’s duct. 
8 The term “submaxillary,” although firmly established by usage, is a misnomer. 
