Part 137

FIG. 326.—TONGUE OF DOG. a, Tonsil; b, vallate papillæ; c, foliate papilla; d, fungiform papillæ; e, median groove of dorsum; f, epiglottis; g, soft papillæ of root; h, middle glosso-epiglottic fold; 1, tip; 2, root. (Ellenberger-Baum, Anat. d. Haustiere.) ]

The =cheeks= are loose and capacious, and their mucous lining is smooth and more or less pigmented. The =parotid duct= opens usually opposite the third upper cheek tooth. Near the last tooth are the openings of the four or five ducts from the orbital gland.

The =hard palate= is widest between the fourth pair of cheek teeth. It has eight to ten curved ridges on either side of the raphé. Behind the first pair of incisor teeth is the triangular incisive papilla, at which the naso-palatine ducts open. The mucous membrane is usually pigmented.

The =soft palate= is thick except at its margins. In the resting state of the parts it comes in contact with the oral surface of the epiglottis. Between its anterior and posterior pillars on either side is a marked tonsillar sinus, in which an elongated =tonsil= is situated; this is reddish in color, about an inch long, and projects somewhat into the fauces between two folds of mucous membrane.

The =tongue= is wide, thin, and very mobile. It is not pigmented, but has a bright red color. The upper surface is marked by a median groove (Sulcus medianus linguæ), and is thickly beset with short, pointed, filiform papillæ, the free ends of which are directed backward. On the root the papillæ are long and soft; similar papillæ occur on the lateral walls of the isthmus faucium. The fungiform papillæ are small, and are scattered over the dorsum and sides of the tongue, but are absent on the root. There are usually two or three vallate papillæ on either side. Small foliate papillæ are also present. In the inferior part of the tip of the tongue is the =lyssa=, a fusiform cord, composed of fibrous tissue, muscular tissue, and fat. In large dogs it is about two inches (ca. 4 to 5 cm.) long.

FIG. 327.—SKULL OF ADULT ST. BERNARD DOG, SCULPTURED TO SHOW THE EMBEDDED PARTS OF THE TEETH.

I1–3, Incisors; C, canines; P1–4, premolars; M1–3, molars. ]

THE TEETH

The formula for the permanent teeth is:

( 3 1 4 2 ) 2 ( I - C - P - M - ) = 42 ( 3 1 4 3 )

All of the teeth have short crowns and distinct necks; they erupt rapidly. The crowns are white, being destitute of cement.

The =incisors= are placed almost vertically and close together in the jaw-bones. They do not correspond to an opposing tooth, but rather to parts of two teeth of the other jaw. The crowns are trituberculate, the central projection being the largest. They increase in size from the first to the third. The labial surface is convex, the lingual slightly concave, and marked off from the neck by a =V=-shaped ridge, the cingulum. The roots are flattened transversely. The lower incisors are smaller than the upper ones. One or two supernumerary teeth may be present.

FIG. 328.—BASE OF SKULL OF COCKER SPANIEL.

I1–3, Incisors; C, canine; P1–4, premolars; M1–2, molars. Note the crowding of the canines and premolars on account of the shortness of the jaw. ]

The =canine teeth= are large, conical, and curved. The upper canine is separated from the corner incisor by an interval into which the lower canine is received when the jaws are closed. The lower canine is close to the corner incisor. The root is about an inch (ca. 2 to 3 cm.) long and is flattened laterally.

The =cheek teeth= are typically ⁶⁄₇, but in brachycephalic breeds they are commonly reduced to ⁵⁄₇, and in extreme cases even to ⅘. The reduction occurs at either end or at both ends of the series. The first tooth appears only once. The fourth tooth of the upper row and the fifth of the lower row are much larger than the rest, and termed =sectorial= or =carnassial= teeth. From these the teeth diminish in size both forward and backward. The upper and lower teeth do not correspond, but rather dovetail. The teeth behind the sectorial ones are tuberculate, i. e., have rounded eminences on the masticatory surface. The others are all sectorial in character, i. e., have sharp-edged, pointed projections, the middle one being the most prominent. The premolars are laterally compressed, and are separated by intervals from the canines and from each other, except in the brachycephalic breeds. The upper molars have wide, somewhat quadrangular crowns, and three roots. The crown of the upper fourth premolar (Dens sectorius) is divided into two pointed lobes and has an antero-internal tubercle; it has three roots. The crown of the first lower molar (Dens sectorius) is compressed laterally and has two pointed, sharp-edged lobes, behind which are one or two tubercles; it has two roots.

FIG. 329.—DISSECTION OF HEAD OF DOG, SHOWING SALIVARY GLANDS, ETC.

a, Ocular muscles; b, pterygoideus internus (cut); c, stylo-glossus; d, digastricus (cut); e, genio-glossus; f, genio-hyoideus; g, hyo-glossus; h, thyro-pharyngeus; i, crico-pharyngeus; k, thyro-hyoideus; l, zygomatic process of temporal (sawn off); 1, parotid gland; 2, submaxillary gland; 3, posterior part of sublingual gland; 3′, anterior part of same; 4, submaxillary duct; 5, ductus sublingualis major; 6, palatine glands; 7, orbital or zygomatic gland; 8, ducts of 7; 9, lacrimal gland. (Ducts colored red.) (After Ellenberger, in Leisering’s Atlas.) ]

The average periods of eruption are given below.

Tooth Eruption │ Change │ I{1} 4 to 5 weeks │4 to 5 months I{2} 4 to 5 weeks │ „ I{3} 4 weeks │ „ C 3 to 4 weeks │4 to 5 months P{1} 4 to 5 months│5 to 6 months P{2} 4 to 5 weeks │ „ P{3} 3 to 4 weeks │ „ P{4} 3 to 4 weeks │ „ M{1} 4 months │ upper 5 to 6 │ M{2} months │ lower 4 ½ to │ 5 months │ M{3} 6 to 7 months│

THE SALIVARY GLANDS

The =parotid gland= is small. Its upper part is wide and is divided into two lobes by a deep notch into which the base of the ear is received. The lower end is small and overlaps the submaxillary gland. The =duct= leaves the gland at its anterior border, crosses the masseter muscle, and opens into the mouth opposite the third upper cheek tooth. Small accessory glands (Glandulæ parotidæ accessoriæ) are sometimes found along the course of the duct.

The =submaxillary gland= is usually larger than the parotid. In large dogs it is about two inches (ca. 5 cm.) long and an inch or more (ca. 3 cm.) wide. It is rounded in outline and of a pale yellow color. Its upper part is covered by the parotid, but it is otherwise superficial, and is palpable in the angle of junction of the jugular and external maxillary veins. The =duct= leaves the deep face of the gland, passes along the surface of the digastricus and stylo-glossus, and opens into the mouth near the frenum linguæ on a very indistinct papilla.

FIG. 330.—SAGITTAL SECTION OF PHARYNGEAL AND LARYNGEAL REGIONS OF DOG.

1, Œsophagus; 2, larynx; 3, mouth cavity; 4, epiglottis; 5, arytenoid cartilage; 6, soft palate; 6″, position of soft palate when raised; 7, vomer; 8, base of cranium; 9, root of tongue; a, a′, a″, pharynx; b, fornix of pharynx; c, posterior wall of pharynx; d, floor of pharynx; e, pharyngeal surface of soft palate; f, origin of œsophagus; g, vestibule of larynx; h, isthmus faucium; i, Eustachian opening; k, posterior naris. (After Ellenberger, in Leisering’s Atlas.) ]

The =sublingual gland= is divided into two parts. The posterior part (Glandula sublingualis grandicanalaris) lies on the digastricus muscle in intimate relation with the submaxillary gland, but clearly separable from it after removal of the common fibrous capsule. It has a pointed anterior process. The =duct= (Ductus sublingualis major) accompanies the submaxillary duct, and usually opens beside it, but in some cases joins it. The anterior part (Glandula sublingualis parvicanalaris) is long and narrow; it lies on the stylo-glossus muscle. It has a number (8 to 12) of small ducts (Ductus sublinguales minores), some of which open directly into the mouth, while others join the large duct.

The =orbital= or =zygomatic gland= (Glandula zygomatica) represents the superior molar glands of herbivora. It is prismatic and is situated in the orbital region, between the zygomatic arch and the internal pterygoid muscle, in contact with the periorbita. It has four or five =ducts= (Ductus zygomatici) which open near the last upper cheek tooth; one of them (canal of Nuck) is almost as large as the parotid duct; the others are small.

THE PHARYNX