Part 56

3. The =sublingual gland= is elongated and conical in form, with its base against the submaxillary, of which it appears to be a continuation. It stretches along the submaxillary duct for about one and one-half centimeters, lying between the masseter and digastric muscles. The =sublingual= duct leaves its ventral side, passes close to the submaxillary duct, at first dorsad and then mediad of it, and opens on the medial side of the apex of the same papilla with the submaxillary duct.

4. =The molar gland= (=glandula molaris=) (Fig. 65, 9) lies between the orbicularis oris and the mucosa of the lower lip. It stretches from the cranial border of the masseter to a point between the first premolar and the canine. It is flat, broad caudad, and ends in a point craniad. It has several ducts which pass straight through the cheek and open on the mucous surface of the mouth.

5. The =infraorbital= (or =orbital=) =gland= lies in the lateral part of the orbit on its ventral floor. It is ovoid and about one and one-half centimeters long and one-third as thick. Its ventral end rests against the mucosa of the mouth just caudad of the molar tooth. Its duct leaves the ventral end and opens into the mouth at a point about three millimeters caudad of the molar tooth.

THE TEETH. DENTES.--The adult cat has thirty teeth, fourteen in the lower jaw and sixteen in the upper jaw. There are twelve =incisors=, four =canines=, ten =premolars=, and four =molars=. The tooth formula for the cat is then

3 - 3 1 - 1 3 - 3 1 - 1 i-----, c-----, pm-----, m-----. 3 - 3 1 - 1 2 - 2 1 - 1

The teeth are implanted in the alveolar borders of the premaxillaries, maxillaries, and mandible. In each tooth can be distinguished the =root=, imbedded in the socket of the bone, the =crown=, which projects above the gums, and a narrow =neck= connecting the two. The root is composed of one or more separate fangs; the crown bears one or more points or cusps.

At the cranial end of each jaw are six =incisor= teeth (Figs. 93 and 94, a). These are imbedded in the alveolar borders of the premaxillaries and the mandible. The incisor teeth are small, with a crown bearing a sharp edge which is notched so as to form three minute cusps. The root of each has a single fang. The lateral incisors are the largest in each jaw, and those of the upper jaw are larger than those of the lower.

a, incisors; b, canine; c, first premolar; d, second premolar; e, third premolar; f, molar.]

Caudad of the incisors, and in the upper jaw separated from them by a slight interval, are the =canines= (b), two in each jaw. These are long, strong, pointed teeth, deeply imbedded in the mandible and maxillaries, their large sockets causing a rounded swelling on the external surface of the bones. Each has a single fang and a single cusp. When the mouth is closed the upper canines lie laterocaudad of the lower ones.

Caudad of the canines there is in each jaw a considerable interval free from teeth: this is called the =diastema=. Caudad of the diastema are the =premolar= teeth, three pairs (c, d, e) in the upper jaw and two pairs (c, d) in the lower jaw. These teeth are compressed sideways, and those of the lower jaw fit inside of those of the upper jaw. In the =upper= jaw (Fig. 93) the first premolar (c) is small and usually has but a single cusp and a single fang, though occasionally there is a small supplementary cusp and fang. The second premolar is larger (d); it has a large central cusp, with a single smaller cranial cusp and two small caudal cusps, making four in all. This tooth has two fangs. The third premolar (e) is the largest tooth in the jaws; it has three large cusps in longitudinal series and a small cusp lying on the medial side of the first one in the row. Its root has three fangs. The =molar= tooth (f) of the upper jaw is small and lies caudomediad of the last premolar. It has two small cusps and two fangs.

a, incisors; b, canine; c, first premolar; d, second premolar; f, molar.]

In the =lower= jaw (Fig. 94) the two premolars (c and d) are similar, the caudal one being a little larger. Each has four cusps; a single large one, a small one craniad of this, and two small ones caudad of it. Each has two fangs. The single molar (f) is the largest tooth of the lower jaw; it has two large cusps and two fangs.

=The Deciduous Teeth.=--At birth the cat has no teeth. There appears later a set of twenty-six teeth: twelve incisors, four canines, and ten molars (six in the upper jaw and four in the lower). These teeth are later replaced by the permanent ones above described. The deciduous teeth of the cat are fully described by Jayne (“Mammalian Anatomy,” vol. 1. p. 319), where also an account is given of the order of appearance of the teeth.

THE TONGUE. LINGUA (Fig. 95).--The =tongue= is a muscular organ covered with mucous membrane; in life it is very mobile. It is an elongated organ, flat above, broadest in the middle, and very slightly narrowed at each end. It extends from the incisor teeth to the isthmus faucium and nearly fills the mouth cavity. The caudal third of the tongue forms the floor of the mouth cavity, so that the tongue has here no ventral surface, but is directly continuous with underlying organs. It is in this region that the extrinsic muscles of the tongue (except the genioglossus) enter it. The cranial two-thirds of the tongue is partly or entirely free from the floor of the mouth, the cranial one-third being completely free and movable. In about the middle third the ventral surface of the tongue is held to the floor of the mouth by the fold known as the =frenulum linguæ=. The frenulum contains parts of the two genioglossus muscles, which enter the tongue through it. The ventral surface and lateral borders of the tongue are smooth, soft, and free from papillæ. The dorsal surface is raised into papillæ of various kinds, and has a slight median longitudinal furrow. The caudal part of the dorsal surface is softer, redder, and marked with papillæ of a different kind from those of the rest of the tongue. From the caudal end a small median vertical fold, the =frenulum= (or =plica=) =glossoepiglottica= passes from the dorsal surface of the tongue to the cranial surface of the epiglottis.

a, filiform papillæ; b, fungiform papillæ; b′, very large papillæ at the sides of the tongue; c, circumvallate papillæ; d, tonsils; e, epiglottis; f, plica aryepiglottica; g, arytenoid cartilages (covered with mucosa); h, glottis; i, false vocal cords; j, true vocal cords.]

The =papillæ= of the tongue are of three kinds. 1. The very numerous =filiform papillæ= (a) (=papillæ filiformes=); many of them are horny and tooth-like, with points turned caudad. These are most numerous at the middle of the free end of the tongue. 2. The =fungiform papillæ= (b) (=papillæ fungiformes=) are found scattered over the surface of the middle of the tongue caudad of the large filiform papillæ. They are enlarged at their free ends. There is a prominent row of very large ones (b′) opposite the circumvallate papillæ at the borders of the tongue. 3. The =circumvallate papillæ= (c) (=papillæ vallatæ=) are blunt and each is surrounded by a trench which is bounded in turn by a raised wall. They are in two rows of two or three each, which converge near the base of the tongue so as to form a V with the apex directed caudad.

MUSCLES OF THE TONGUE (Fig. 96).--=M. genioglossus= (f) passes from the symphysis of the lower jaw into the tongue and lies beneath (dorsad of) the geniohyoid (g).

Origin from the medial surface of the mandible near the symphysis and dorsad of the origin of the geniohyoid.

Insertion.--The fibres pass dorsad, diverging in a fan-like manner and forming a flat vertical plate closely applied to the muscle of the opposite side. This plate extends along the caudal three-fourths of the tongue, i.e. as far as it is attached. The cranial fibres arch craniad to the tip of the tongue, the caudal fibres arch caudad to the root of the tongue. Dorsad the muscle is confounded with the muscle of the opposite side.

Action.--Draws the root of the tongue forward and the tip backward.

=M. hyoglossus= (h).--From the body of the hyoid bone to the tongue.

Origin.--(1) From the ventral surface of the body of the hyoid laterad of the geniohyoid (g), and (2) by a second head from the ceratohyal.

Insertion.--Both heads penetrate into the tongue between the styloglossus (e) and the genioglossus (f). The fibres intermingle with those of the styloglossus (e) and thus help to form the lateral parts of the tongue. They finally end in the integument on the dorsum of the tongue at the sides.

Action.--Retracts the tongue and depresses it.

=M. styloglossus= (e).--From the stylohyal bone to the tongue.

Origin from the mastoid process of the temporal bone, from the stylomandibular ligament (2) (which connects the border of the external auditory meatus with the angular process of the mandible) and from the proximal cartilaginous portion of the cranial cornu of the hyoid bone. The fibres pass mediad, diverging between those of the digastric and hyoglossus (h) into the lateral part of the tongue.

Insertion.--The fibres pass toward the tip of the tongue, where the mass finally ends in a point, the superficial ones gaining insertion into the integument at the sides of the tongue.

Relations.--Outer surface with the digastric (Fig. 65, b) and mylohyoid (Fig. 65, c). Inner surface with the pterygoideus internus (Fig. 96, d), the cranial cornu of the hyoid, and the tympanic bulla.