Openings of the Ducts of Rivinus,-8 to 18 on each side from the sublingual glands, near the frenum of the tongue. The longest is the Duct of Bartholine, which opens into the duct of Wharton.

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Where are the Salivary Glands? The Parotid Gland1 lies below and in front of the external ear,-the Sub-maxillary and Sub-lingual Glands lie in the corresponding fossa on the inner surface of the inferior maxillary bone. [See Fig. 66.]

Describe the Tongue. The tongue consists of extrinsic and intrinsic muscles, a hyo-glossal membrane and a mucous membrane, a median fibrous septum, vessels and nerves. Its Base is attached to the hyoid bone, the epiglottis, the soft palate and the pharynx. Its Under Surface is attached to the hyoid bone and the inferior maxillary. Its mucous membrane is reflected over the floor of the mouth to the inner surface of the gums, forming in front a fold, the Frenum Lingua.

The Tongue presents

Filiform Papilla, along its sides, closely packed in rows.

Fungiform Papilla,2 scattered over the anterior two-thirds of its dorsum. Circumvallate Papilla,1 7 to 12 in number, in two rows, forming a V at the base of the tongue, meeting at the Foramen Cacum, which contains the central papilla. FIG. 67.

Follicular Glands, posteriorly to the circumvallate papillæ.

Racemose Glands, over the dorsum, sides, and

under surface. Beneath the tip they form

two small oblong masses.

Extrinsic Muscles, are the stylo-, hyo-, geniohyo-, and palato-glossus muscles. [See pp. 73, 74.]

Intrinsic Muscles, are the several fibres of the lingualis muscle,-superior, inferior, transverse and perpendicular.

Name the Arteries of the Tongue. They are the

Lingual, branch of the external carotid,-with its branches, the

Dorsalis linguæ. Sub-lingual. Ranine.

Sub-mental, branch of the facial,-anastomoses

with the sub-lingual.

Ascending Pharyngeal, branch of the external carotid, sends some small branches to the pharynx and tongue.

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What Nerves are distributed to the Tongue? The

Gustatory Branch of the 5th,-to the mucous membrane of the sides and anterior two-thirds of the tongue, endowing it with general sensibility. Chorda Tympani Branch of the 7th,-joins the gustatory, and is distributed to the same region, being the nerve of taste for the anterior two-thirds of the tongue.

Lingual Branches of the 9th or Glosso-pharyngeal,—to the mucous membrane of the base and sides of the tongue, being the nerve of taste for its posterior third.

Hypoglossal, or 12th,—to the intrinsic and extrinsic muscles of the tongue, being its nerve of motion.

Superior Laryngeal Branch of the 10th or Pneumogastric,—sends a few fibres to the base of the tongue from its internal branch.

What special Anatomical Features are presented by the Mouth? They are as follows, viz.-the

Hamular Process of the Sphenoid Bone,-may be felt behind the last upper molar tooth; also the Internal Pterygoid Plate, and part of the Pterygoid Fossa.

Coronoid Process,-of the lower jaw, its anterior border.

Posterior Palatine Artery,—at inner side of the last upper molar tooth, and in front of the hamular process.

Gustatory Nerve,-very near the last lower molar tooth.

Pterygo-maxillary Ligament,—felt as a fold posteriorly to the last lower molar tooth.

THE PHARYNX.

Describe the Pharynx. It is a conical, musculo-membranous bag, about 41⁄2 inches long, hung base up from the basilar process of the occipital bone, and extending to the lower border of the cricoid cartilage posteriorly, or the 5th cervical vertebra, where it becomes continuous with the oesophagus. 5. It forms the part of the alimentary canal which lies behind the mouth, being incomplete in front.

What are its Relations? It is connected with

Posteriorly, the longus colli and recti capitis antici muscles, and by loose areolar tissue to the first 5 cervical vertebræ.

Laterally, the styloid processes and their muscles, the pterygoid muscles, the internal carotid arteries, the internal jugular vein, the 8th, 9th, and the sympathetic nerves.

Near its Apex,-the lobes of the thyroid gland, the common carotid and lingual arteries, the sterno-hyoid muscle, and the lingual nerves.

Describe its Structure. The pharynx is composed of 3 coats,- -a mucous, a muscular and a fibrous, the latter lying between the other two, and sometimes called the Pharyngeal Aponeurosis. The mucous coat is covered with ciliated columnar epithelium above the level of the floor of the nares-below that level by squamous epithelium; and contains simple follicular glands, also compound follicular and racemose glands, the latter being most numerous in the upper part, between the two Eustachian tubes.

Name its Muscles, Arteries and Nerves. Its

Muscles, 5,-are the Superior, Middle and

Inferior Constrictors, Stylo-pharyngeus, and Palato Pharyngeus. [See pages 73, 74.] Arteries number 4, as follows,

Superior Thyroid Branches.

Branches of

Ext. Carotid.

Nerves,-Branches of the Pharyngeal Plexus, which is formed by the pharyngeal branches of the pneumogastric, glosso-pharyngeal, superior laryngeal, and superior cervical ganglion of the sympathetic.

THE ESOPHAGUS.

Describe the Esophagus. It is a musculo-membranous tube, about 9 inches long, extending from the 5th cervical vertebra and the lower border of the cricoid cartilage of the larynx, through the oesophageal opening in the

diaphragm to the cardiac orifice of the stomach, opposite the 9th dorsal vertebra, where it terminates. It lies in the neck, between the trachea and the vertebral column, resting in part on the longus colli muscle; then inclining to the left side it reaches the posterior mediastinum behind the left bronchus.

Describe its Structure. The Esophagus has three coats, a—

Mucous, in thick longitudinal folds, containing compound racemose glands, and covered with a thick layer of squamous epithelium.

Cellular,-forms a loose connection between the other two coats, and contains the oesophageal vessels.

Muscular, having longitudinal fibres externally, circular fibres internally, which are continuous with the fibres of the stomach below, and with those of the inferior constrictor muscle above.

Name its Vessels and Nerves. The Esophageal— Arteries, are chiefly branches from the thoracic aorta.

Veins, empty into the vena azygos minor.

Nerves, are branches of the pneumogastric and the cervical sympathetic, forming the Esophageal Plexus.

THE STOMACH.

Describe the Stomach. It is the principal organ of digestion, pyriform in shape, of musculo-membranous structure, about 12 inches long by 4 inches in average diameter, held in position by the lesser omentum, and situated diagonally across the upper abdomen, in the epigastric and right and left hypochondriac regions, above the transverse colon, below the liver and diaphragm. It presents for examination a

Fundus or Splenic End, c-connected to the spleen by the gastro-splenic omentum. (See under PERITONEUM.)

FIG. 69.

Pylorus or Lesser End,-lies

in contact with the anterior Iwall of the abdomen, the under surface of the liver, and the neck of the gallbladder, its position being near the end of the cartilage of the 8th rib. Greater Curvature,d-is convex, and is connected to the colon by the gastro-colic omentum. (See under PERITONEUM.)

Lesser Curvature, i-is concave, and connected to the liver by the gastrohepatic omentum, and to the diaphragm by the gastro-phrenic ligament. Esophageal Orifice, b—is situated between the fundus and the lesser curvature. It is funnel-shaped, and the highest part of the organ.

Pyloric Orifice, k—opens into the duodenum, and is guarded by the circular muscular fibres of the pylorus, which are aggregated into a circular ring, projecting into the cavity, and with its covering fold of mucous membrane, forming the Pyloric Valve.

Describe its Structure. The Stomach has 3 coats, a—

Mucous Coat, 8-lined with columnar non-ciliated epithelium, covered with polygonal Alveoli, † of an inch in diameter, containing the orifices of the Gastric Follicles. When the stomach is contracted the mucous membrane lies in longitudinal folds or Ruga, h one of which aids in forming the valve at the pyloric orifice.

Cellular or Sub-mucous Coat,—contains the gastric vessels.

FIG. 70.

Muscular coat,f-consists of longitudinal, circular, and oblique fibres. The Longitudinal are continuous with those of the oesophagus and small intestine, and are the most superficial. The Circular lie deeper, and over the whole organ; they form a sphincter valve around the pyloric orifice. (See above.) The Oblique Fibres lie deepest, forming two sets around the oesophageal opening, in continuation of the circular fibres of the oesophagus.

THE SEROUS INVESTMENT of the stomach is derived from the peritoneum, and covers the whole external surface, excepting the points where the gastro-splenic,

greater and lesser omenta

are attached. It is usu

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ally, but incorrectly, described as a fourth coat of the stomach.

Describe the Gastric Glands. They are of 3 kinds, the

Peptic Follicles,-situated all over the stomach, but most numerous towards the splenic end,-are tubules lined with columnar epithelium in their upper one-fourth, and filled with nucleated cells in their deepest parts.