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tongue are due to muscular action. Any physiologist who has felt the firm but regulated grasp of the tongue of the Giraffe, when twined round the finger, must have recognised the difference of the action from the fitful force arising from vascular or erectile injection. The muscular fibres in the free and flexible part of the tongue present an arrangement adequate to all its movements. The stylo-glossi and inferior linguales expand into a layer of longitudinal fibres, about a line in thickness, covering the whole of the inferior surface of the free portion of the tongue, and becoming continuous at the sides, with a corresponding but thicker stratum of longitudinal fibres on the upper surface of the tongue; these longitudinal muscles inclose a mass of fibres, which run in the transverse direction. The action of the transverse, combined with that of several short vertical, fibres near the margins, and of those forming the thin circular stratum surrounding the stylo-glossi at the middle part of the tongue, serves to attenuate or diminish the transverse diameter of the tongue and increase its length; while thus rigidly extended the apex of the tongue can be curved upward or downward by the superficial longitudinal fibres, which are less intermingled with the transverse fibres than in the tongues of most other Mammals: the contraction of the longitudinal fibres taking place with the relaxation of the transverse ones produces the retraction of the whole organ. The nerves of the tongue present the same disposition as those in ordinary Ruminants, but the ninth pair is relatively larger than the branch from the fifth pair; the nerve which runs along the inner or under surface of the stylo-glossi toward the free extremity of the tongue is remarkable for its beautifully wavy course, by which it is accommodated to the variations which occur in the length of the organ in the living animal.

The back of the mouth appears to be as completely closed in the Giraffe as in the Capybara; but, instead of contracting, like a funnel, to a small circular depression, it terminates by a transverse slit, through which projects the broad upper margin of the epiglottis, which is folded upon itself. The faucial membrane is coarsely corrugated. The velum palati descends to the interspace between the epiglottis and the large arytenoid cartilages; and there is an uvular process from the middle of the inferior margin. The tonsils are well-developed glands of a flattened oval form, having each a short duct communicating by one wide opening with the fauces.

xvII'. pl. xlii, fig. 3.

The back of the mouth, in Ruminants, presents its chief modifications in the Camel-tribe. A broad pendulous flap hangs down from the fore part of the soft palate and usually rests upon the dorsum of the tongue. The velum palati extends beyond this process, some way down the pharynx and terminates by a concave border. The pharynx behind the velum dilates into a sac. In the rutting male the palatal flap is greatly enlarged. I have found it extending ten inches down the pharynx, passing below the margin of the soft palate and the opening of the larynx, into the œsophagus: in the living animal it is, at this season, occasionally protruded, with a belching noise, from the mouth. Its surface shows the pores of innumerable mucous crypts, and in the ordinary state, in both sexes, the flap may apply its own secretion, and water regurgitated from the storage-cells of the stomach, to the extended surface of the pharynx and root of the tongue, so as to allay the feeling of thirst and help the animal to endure the long remissions of drinking to which it is liable in traversing the desert.

The mouth in Carnivora is characterised by the width of its gape, and the mobility, dilatability, and contractility of its muscular and membranous walls. Check-pouches have not been found in any species. The great extent of faucial membrane between the back of the tongue and the larynx, with the coextensive soft palate in the Lion and some other large Felines, has been adverted to (p. 198); also the retroverted spines, and the lytta of the tongue in connection with the work of the mouth, in certain Carnivora. In the Hyæna the tonsils are relatively larger than in the Lion. The palatal gum is transversely ridged in most Carnivora. The provision for the lubricating mucus at the back of the mouth and fauces is much less in the present than in the hoofed group of Mammals.

In Quadrumana the Cercopitheci, Macaci, and Cynocephali have cheek-pouches, the slit-like orifices of which are a little within the labial commissure; the cavity extends outside and below the mandibular rami, where it is occasionally seen much distended with food. The Semnopitheci and Colobi, remarkable for their large sacculated stomachs, have not such cheek-pouches : they are wanting also in Lemurida, Platyrhines, and tailless Apes.

The Lemurida have the palatal gum ridged. In the Aye-aye' there are three curved transverse ridges anteriorly, convex forward, followed by four transverse pairs of similar ridges. In other Lemuride the palatal ridges are similarly curved, but cu'. p. 41, pl. xii, fig. 6.

usually undivided, from five (Potto) to eight or nine (Galago) in number: between the two anterior ridges are the orifices of canals leading from the palate to the nose.

The uvula is represented in the Aye-aye and some other Lemuride by a medial longitudinal fold from the back of the soft palate close to the margin, but does not project so as to divide the fauces into two arches: this form of soft palate begins to appear in Platyrhines: in the Baboons the uvula is thick and short: in the Apes it approaches nearer the proportions of that appendage in Man.

In the higher Quadrumana the palate is smooth, or unridged, as in Man.

§ 224. Salivary Glands.-Fluids of different properties are poured into the mouth in aid of its various functions of receiving, retaining, comminuting, softening or dissolving, tasting, and transmitting throatward, the food. For the preparation of these fluids corresponding modifications of glandular parts exist, from the simple mucous follicle to aggregates of three or of more complex follicles, with further multiplication and compaction of secerning surfaces, in groups and bodies, forming glands and ducts with definite names.

As the function of the mouth is simplified so is the condition. of such ministering glands. In the piscivorous Cetacea, which bolt their food like fishes, the parotids and submaxillaries are not present: the latter are represented with the sublinguals, in a diffused form in whalebone whales. The parotids are large in Sirenia; their ducts open in the Manatee on two papillæ, one on each side the fore part of the palate: in the Dugong the parotids are situated immediately behind the ascending mandibular rami: there is a thick layer of mucous glands above the membrane covering the hard palate.

In the Ornithorhynchus the parotid, fig. 3, E, is divided into flat portions or lobes thinly applied to the fundus of the cheekpouch and anterior to the long meatus auditorius. The submaxillary, ib. D, is a moderately-sized, oval, compact body, situated behind and below the meatus auditorius. The duct passes under the omo-mylo-hyoideus, ib. 10, and then, contrary to the usual mode, begins to be disposed in a series of about twelve close transverse folds, and terminates by a simple aperture at the frænum linguæ. In the Echidna the submaxillary gland, fig. 302, b, is of unusual dimensions: it extends from the meatus audi

' cxvn". p. 29.

torius along the neck, and upon the anterior part of the thorax : it is a broad, flat, oblong lobulated body, narrowest at its anterior extremity, from which the wide duct emerges. When the duct

[merged small][graphic][subsumed][merged small]

has reached the interspace of the lower jaw, it dilates, and then divides into eight or ten undulating branches, which subdivide and ultimately terminate by numerous orifices upon the mem

branous floor of the mouth. This modification of Wharton's duct' appears to be unique. The large size of the glands and the mode in which the secretion is spread over the floor of the mouth relate to the lubrification of the long, slender, and extensible tongue, and to its fitness as an instrument for obtaining the insect food of the spiny Monotreme.

The salivary glands in the carnivorous Dasyures consist of a small parotid and a large submaxillary gland on each side. They do not agree with the dogs in having the zygomatic glands. The submaxillary is placed in front of the neck, so that its duct passes on the dermal side of the tendon of the biventer maxillæ, and terminates half an inch from the symphysis menti. There is a thick row of labial glands along the lower lip. The Opossums and Bandicoots present a similar salivary system. In the Phalangista vulpina there is a sublingual gland on each side of a firm texture, about one inch in length and three lines broad; a roundish submaxillary gland about the size of a hazel-nut; and a broad and flat parotid, larger than in the entomophagous or sarcophagous Marsupials. The parotid glands are relatively larger in the Koala, in which the duct takes the usual course over the masseter and enters the mouth opposite the third true molar, counting backwards. In the Wombat I found the parotid glands very thin, situated upon both the outer and inner side of the broad posterior portion of the lower jaw; the duct passed directly upwards and outwards to the insertion of the sterno-cleido-mastoideus; here it was buried in the cellular substance anterior to that muscle, then turned over the ramus of the jaw, and, pursuing a somewhat tortuous course over the masseter, entered the mouth just anterior to the edge of the buccinator. The submaxillary glands were each about the size of a walnut; their ducts terminated as usual on each side of the frænum linguæ. In the great Kangaroo the parotid is very large, extending from below the auditory meatus three or four inches down the neck : In the Potoroos it reaches as far as the clavicle. In both genera this gland is separated from the submaxillary gland by the submaxillary vein. The sublingual glands are elongate, but of moderate size. The tonsils are small in all the Marsupials, but are not represented in the carnivorous species, as in the placental Feræ, by simple glandular pouches at the sides of the fauces; for example, they consist of an oblong glandular body on each side in the Dasyurus macrurus.

In Rodents, as in Marsupials, the proportions of the parotid and submaxillary differ according to the nature of the food. In the

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