404 DIGESTI^'E 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 

 subungual. 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 

 ear. Its length is about eight to ten inches (ca. 20 to 25 cm.), and its average thick- 

 ness nearly an inch (ca. 2 cm.). Its average weight is about seven ounces (ca. 

 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 masscter, 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 

 arterj' 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 lea\'es 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 cm.), 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 

 hj^oid 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 cm.), its width an inch 

 to an inch and a half (ca. 2.5 to 3 cm.), and its thickness about half an inch (ca. 

 1 cm.). It weighs about one and a half to two ounces (ca. 45 to 60 g.). It is often 



' In some cases there is a well-marked triangular facial process, which covers the temporo- 

 mandibular joint, the facial nerve, and the transverse facial vessels. 

 ' Formerly known as Stenson's or Steno's duct. 

 ' The term "submaxillary, " although firmly established by usage, is a misnomer. 



