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The papillae found on the anterior two-thirds of the tongue are of three
kinds, circumvallate, funyiform, and conical, varying both in size and form, but all
of them visible to the naked eye ; they themselves, like the rest of the mucous

1 For their developmental significance, see Vol. I., Part 1, Embryology, p. 102.



6



OKGAN8 OF DIGESTION.



membrane of the tongue and mouth generally, are covered \vith closely set, micro-
scopic secondary papillae hidden under the epithelium, which correspond with those
of the skin, and are each occupied by a long loop of capillary blood-vessels.
Lymphatics also originate within the papillae and pass as elsewhere in the mouth
into a superficial plexus in the mucous membrane, from which again the lymph is
conveyed away by valved vessels seated in the submucous tissue.

The circumvallate papilla (fig. 7, 1, 2}, from 7 to 12 in number, are found at
the union of the middle and posterior thirds of the tongue, arranged in two lateral




OF CIRCUMVALLATE

(Engelmann.) 25



Fig. 8. VERTICAL SECTION

PAPILLA FROM THE CALF.

diameters.

A, the papilla ; B, the surrounding wall. The
figure shows the nerves of the papilla spreading
towards the surface, and towards the taste-buds
which are imbedded in the epithelium at the sides ;
in the sulcus on the left the duct of a gland is seen to
open.

rows, which run obliquely backwards and
inwards towards a median papilla, like the

arms of the letter V. Not unfrequently there are two papillae in the middle line.
They are situated in cup-like depressions of the mucous membrane, and have the
shape of a truncated cone, of which the smaller end is attached to the bottom of the
cavity, and the broad flattened base appears on the surface (fig. 8). They are, there-
fore, surrounded by a circular trench (fossa), around which again is a slight annular
elevation of the mucous membrane (vallum). In some of them there is found a
central depression. The ducts of one or more serous glands open into the trench of
each circumvallate papilla (fig. 8, d ; fig. 9, J/). The stratified epithelium covering
the papilla vallata is thick, and completely conceals the minute secondary papillae.

Taste-buds are found forming a zone around the sides of these papillae, and in
man and some animals upon the opposed wall of the vallum (fig. 9). Their struc-

Fig. 9. SECTION OF CIRCUMVALLATE PAPILLA,

HUMAN. THE FIGURE INCLUDES ONE
SIDE OF THE PAPILLA AND THE ADJOIN-
ING PART OF THE VALLUM. (Magnified
150 diameters. ) (Heitzmann. )

E, epithelium ; G, taste-bud ; C, corium
with injected blood-vessels : M, gland with
duct.

tnre is given in the part of this
work dealing with the sense organs
(Vol. III., Part 3, pp. 148-151).

The fungiform papilla^ more
numerous than the last, are small
rounded eminences scattered over
the middle and fore part of the
dorsum of the tongue (fig. 7, 3) ;
but they are found in greater num-
ber and closer together at the apex
and near the borders. They are

easily distinguished in the living tongue owing to their deep red colour. They are

narrow at their points of attachment, but are gradually enlarged towards their free

extremities, which are blunt and rounded (fig. 10).

The conical papille are the most numerous of all, as well as the smallest. They

are minute, conical, tapering, or cylindrical eminences, which are densely set over




THE TONGUE.



the greater part of the dorsum of the tongue (fig. 7, 4), but towards the base
gradually disappear. They are arranged in lines diverging from the raphe, at first





Fig. 10. SECTION OF FUNOIPORM PAPILLA, HUMAN, WITH THE BLOOD-VESSELS INJECTED. (Heitzmann.)
E, epithelium ; C, coriura ; L, lymphoid tissue ; M, muscular fibres of tongue.

Fig. 11. A FUNGIFORM PAPILLA WITH THE BLOOD-VESSELS INJECTED. (After Todd and Bowman. )

a, artery ; v, vein ; c, capillary loops of simple papillae in the neighbourhood, covered by the
epithelium ; d, capillary loops of the secondary papilla ; e, epithelium.

in an oblique direction, like the two ranges of papillas vallatae, but gradually becom-
ing transverse towards the tip of the tongue. At the sides they are longer and more
slender, and arranged in parallel rows, perpendicular to the border of the tongue.




Fig. 12. SECTION OF TWO FILIFORM PA-
PILLA, HUMAN. (Heitzmann.)
, epithelium ; 0, corium ; L, lymphoid
tissue ; M, muscular fibres of tongue.

Fig. 13. TWO FILIFORM PAPILLAE, ONE WITH

EPITHELIUM AND WITH THE BLOOD-
VKSSELS INJECTED, THK OTHER WITHOUT.

35 diameters. (After Todd and Bow-
man.)

p, the substance of the papillse divided at their upper extremities into secondary papillae ; a, artery,
and v, vein, connected by capillary loops ; c, epithelial covering, laminated between the papillae, but
extended into hair-like processes, /, over the secondary papillae.




8



ORGANS OF DIGESTION.




The secondary papillae which are borne by some of the conical papillae are
peculiar both in containing a number of elastic fibres, giving them greater firmness,
and in the character of their epithelial covering, which forms a separate horny
process over each secondary papilla, greater in length than the papilla which it
covers (figs. 12 and 13). Over some of the papillae these processes form a pencil of
fine fibres, as shown in fig. 13 ; hence the name "filiform " which has been applied
to these papillae.

The papillary surface of the tongue is supplied abundantly with nerves, some
of which terminate in end-bulbs, and a few in tactile corpuscles. In the fungiform

, Fig. 14. TONGUE OF RABBIT, SHOWING THE SITUATION OF

THE PAPILLA FOLIATE, p.

papillae the nerves are large and numerous ; but
they are still more abundant, and of greater size,
in the circumvallate papillae, where they are chiefly
distributed in the neighbourhood of the taste-buds
(fig. 8).

The papillae, besides being the parts chiefly

concerned in the special sense of taste, also possess, in a very acute degree, tactile
sensibility ; and the conical and filiform papillee, armed with their denser epithelial
covering, serve a mechanical purpose, in the action of the tongue upon the food, as
is well illustrated by the more developed form which these papillae attain in many
carnivorous animals.

In some animals (e.g., rabbit) there is present on each side of the tongue, about opposite
the ends of the V formed by the line of papillae vallatae, an oval aggregation of transversely

Fig. 15. VERTICAL SECTION OF

PAPILLA FOLIATA OF THE
RABBIT, PASSING ACROSS THE

FOLi^E. (Ranvier.)

p, central lamina of the co-
rium ; v, section across a vein,
which traverses the whole length
of the folia ; p', lateral lamina
in which the nerve-fibres run ;
//, taste-bud ; n, sections of nerve-
bundles ; a, serous gland.

placed ridges or lamina? with
intervening furrows, which is
termed the pnpilUi foliata
(fig. 14). The ridges are
covered with a thick stratified
epithelium, and in this epithe-
lium at their sides are em-
bedded numerous taste -buds
(fig. 15). There is no definite
papilla foliata in the human
tongue, but in a situation

similar to that in which the papilla foliata of animals occurs the mucous membrane often

exhibits a number of low ridges, and is beset with taste-buds.

Foramen caecum and thyro-glossal duct. The foramen cEecum is a median
recess, variable in size and sometimes absent, which is situated just behind the
median circumvallate papilla. According to His, it represents the apex of a V-
shaped depression, which is formed by the development of the tongue from an
anterior median process (tuberculum impar), and two lateral and posterior promi-




THE TONGUE. 9

nenccs, which grow forwards at the sides of the tuberculum impar. According to
the same authority, the foramen caecum indicates the position of the epithelial
outgrowth from which the median portion of the thyroid gland hasT>een formed.
As the thyroid recedes from the tongue it becomes connected with the foramen
caecum by a long narrow tube the thyro-glossal duct. The upper part of this duct
may persist as a canal (ductus liiigualis) leading from the foramen caecum downward
to the hyoid bone. Kanthack, on the other hand, holds that no intrinsic connec-
tion exists between the development of the tongue and that of the thyroid body.
He states that the foramen cascum is often absent, and when present passes back-
wards near the surface and never dips down towards the basi-hyoid. In none out of
one hundred adults that he examined did he find any trace of a lingual duct, and
out of sixty foetuses, varying in age from two and-a-half to eight months, he never
observed the foramen cascum to extend downwards to the hyoid bone.

Glands. The mucous membrane of the tongue is provided with numerous
small glands (lingual glands'), collected principally about the posterior part of its
upper surface, near the papillas vallatae and foramen cascum, into which last the
ducts of several open. These glands have usually been supposed to secrete mucus,
but it has been ascertained that some of them, especially those which open in the
trenches around the papillae vallatae, and at other parts where taste-buds occur,
yield a serous secretion (Ebner). Other small glands are found also beneath
the mucous membrane of the borders of the tongue. There is, in particular, a
group on the under surface of the tongue on each side near the apex called the
glands of Blandin (see fig. 5). They are there aggregated into a small oblong mass,
out of which several ducts proceed and open in a line on the mucous membrane.
Most of the glands are acino-tubular.

The mucous membrane of the tongue, at least its posterior part, is largely com-
posed of retiform or lymphoid tissue, which is collected at numerous points into the
denser nodular masses known as follicular glands, or lymphoid follicles. The
blood-vessels and lymphatics of this part of the membrane are numerous and large,
but the papillae on its surface are comparatively small, and are completely concealed
by the thick superjacent epithelium. Here and there the mucous membrane ex-
hibits recesses or crypts (fig. 10,/), either simple or surrounded by smaller ones
which open into them. The walls of these recesses are generally studded with
lymphoid nodules ; and they receive many of the ducts of the mucous glands.

Muscular substance. The substance of the tongue is chiefly composed of
muscular fibres running in various directions. Many belong to muscles which enter at
its base and under surface, and attach it to other parts : these are called the extrinsic
muscles of the tongue (hyo-glossus, chondro-glossus, genio-glossus, palato-glossus,
stylo-glossus), and are elsewhere described. Others which constitute the intrinsic or
proper muscles, and are placed entirely within the substance of the organ, will be
here more particularly noticed. They are as follows :

The superficial lingual muscle consists mainly of longitudinal fibres, placed
near the upper surface of the tongue, immediately beneath the mucous membrane,
and is traceable from the apex of the organ backwards to the hyoid bone (fig. 17, 10 ;
fig. 1(5, I .<?). The individual fibres do not run the whole of this distance, but are
attached at intervals to the submucous and glandular tissues. The entire layer
becomes thinner towards the base of the tongue, near which it is overlapped at the
sides by a thin plane of oblique or nearly transverse fibres derived from the palato-
glossus and hyo-glossus muscles.

The inferior lingual muscle consists of a rounded muscular band, extending
along the under surface of the tongue from base to apex, and lying outside the
genio-glossus, between that muscle and the hyo-glossus (fig. 17, 6). Posteriorly,
some of its fibres are lost in the substance of the tongue, and others reach the hyoid



10



ORGANS OF DIGESTION.



bone. In front, having first been joined, at the anterior border of the hyo-glossus
muscle, by fibres from the stylo-glossus, it is prolonged beneath the border of the
tongue as far as its point.

The transverse muscular fibres of the tongue (fig. 17, # ; fig. 16, tr) form together
with the intermixed fat a considerable part of its substance. They are found in the




Fig. 16. LONGITUDINAL VERTICAL SECTION OF THE TONGUE, LIP, &c. (From Kolliker ami Arnold.)

m, symphysis of the lower jaw'; d, incisor tooth ; h, hyoid bone ; g h, genio-hyoid muscle ; g,
genio-hyo-glossus spreading along the whole of the trmgue ; t r, transverse muscle ; I s, superior longi-
tudinal muscle ; g I, lingual glands ; /, lymphoid crypts ; e, epiglottis ; I, section of the lip and labial
glands ; o, cut fibres of the orbicularis oris ; I m, levator menti.

interval between the upper and lower longitudinal muscles, and they are interwoven
extensively with the other muscular fibres. Passing outwards from the median
plane, where they take origin from a fibrous septum (fig. 17, 5), they reach the
dorsum and borders of the tongue. In proceeding outwards, they separate, and the
superior fibres incline upwards, forming a series of curves with the concavity upwards.

Fig. 17. CORONAL SECTION OF THE TONGUE

ABOUT THE MIDDLE OF ITS LENGTH, LF.FT
HALF SEEN FROM BKHIND. (W. KraUSC. )

1, papillae on the dorsal surface ; 2, trans-
verse muscular fibres ; 3, septum linguae ; 4,
gcnio-glossus ; 5, ranine artery ; 6, inferior lin-
gualis ; 7, hyo-glossus ; 8, vertical muscular
fibres; 9, stylo-glossus; 10, superficial lingual
muscle.

The fibres of the palato-glossus muscle
are stated by Zaglas and Henle to be
continuous with fibres of the transverse
set.

Vertical fibres (external perpen-
dicular muscle of Zaglas), decussating
with the transverse fibres and the in-
sertions of the genio-glossus (fig. 17, 8),
form a set of curves in each half of the
tongue with their concavity outwards,

and extending down and out from the dorsum to the under surface of the border, so

that those which are outermost are shortest.




THE PALATE. 11

Examined in transverse sections, the muscular fibres are seen to be arranged so as to render
the substance divisible into an outer part or cortex and an internal or mrilnUartj part. The
fibres of the cortex are principally longitudinal, derived superiorly from the lingualis
superior, further outwards from the hyo-glossus, on the side from the stylo-glossus, and
beneath this from the lingualis inferior. They ensheath the medullary part on all sides
except inferiorly, where the genio-glossi muscles enter it between the inferior linguales. In
the medullary part are found, embedded in fat, the decussating fibres of the transverse
muscle passing across, the genio-glossi radiating upwards and outwards, and the vertical
muscles arching downwards and outwards. In addition to the movements which may be
given to the tongue by the extrinsic muscles, this organ is capable of being curved upwards,
downwards, or laterally by its cortical fibres, it is flattened by the vertical fibres, and its
margins are again drawn together by the transverse whilst the two last mentioned, acting
together, would tend to lengthen the organ.

The septum of the tongue is a thin fibrous partition which extends forwards
from the hyoid bone to the tip, and divides one half of the medullary part of the
tongue from the other, but does not penetrate into the cortex.

Vessels and nerves. The arteries of the tongue are derived from the
lingual, with some small branches from the facial and ascending pharyngeal. The
veins empty their contents into the internal jugular trunk.

The nerves of the tongue (exclusive of branches from the sympathetic nerves)
are five, viz., the lingual branch of the fifth pair, which supplies the papillae and
mucous membrane of the fore part and sides of the tongue to the extent of about
two-thirds of its surface with common sensibility ; the chorda tympani, which
accompanies the lingual to the tongue and probably serves as the nerve of taste to
a corresponding area of the mucous membrane ; the lingual branch of the glosso-
pharyngeal, which sends filaments, both sensory and gustatory, to the mucous
membrane at the base of the tongue, and especially to the papillae vallatae ; the
superior laryngeal, which distributes a few sensory branches in the neighbourhood of
the epiglottis ; and lastly, the hypoijlossal nerve, which is distributed to the muscles.
Microscopic ganglia exist upon the expansions of the glosso-pharyngeal nerve,
especially in the neighbourhood of the papillse vallatas and papillae foliatae, and they
have also been found in the sheep and calf upon the gustatory division of the fifth.

Lymphatics. The chief lymphatic trunks accompany the ranine vessels, and
after traversing one or two small lymphatic glands, seated on the hyo-glossus
miiB'ile, pass into the deep cervical glands. Others pass through the mylo-hyoid
muscle to the submaxillary lymphatic glands.

The detailed description of the blood-vessels will be found in Vol. II., Part 2, and of the
nerves in Vol. III., Part 2.



THE PALATE.

The roof of the mouth is formed by the palate, which consists of two portions ;
the fore part being named the hard palate and the back part the soft palate. As a
whole, the palate is concave from before backwards, and also from side to side.

The hard palate is bounded in front and at the sides by the alveolar arches and
gums, and is. distinguished from the soft palate by having an osseous framework,
already described (see Vol. II., Part 1). It is covered by periosteum and
mucous membrane, these two structures being firmly connected together. In front
the mucous membrane is thick, dense, rather pale, and corrugated, but it becomes
thinner, smoother, and of a deeper colour behind. The corrugations of the mucous
membrane palatal n/gce may be divided into the longitudinal and the trans-
verse. In the middle line there is a longitudinal ridge or raphe, ending behind the
interval between the two mesial incisors in a small eminence, the papilla palatina or




Fig. 18. MEDIAN SECTION OF THE HEAD AND NECK, (liraune.) |

1, sphenoidal sinus ; 2, lateral recess of pharynx ; 3, phaiyngeal orifice cf Eustachian tul>e ; 4,
anterior arch of atlas ; 5, soft palate ; 6, body of axis ; 7, oral portion of pharynx ; 8, epiglottis ; 9,
arytenoid muscle ; 10, cricoid cartilage ; 11, trachea : 12, oesophagus ; 13, origin of innominate artery
from aorta ; 14, genio-glossus muscle ; 15, genio-hyoid muscle ; 16, mylo-hyoid muscle ; 17, platysma ;
18, hyoid bone ; 19, thyroid cartilage ; 20, cricoid cartilage ; 21, isthmus of thyroid body ; 22, sterno-
hyoid ; 23, sterno-thyroid ; 24, left innominate vein ; 25, manubrium stcrni.



THE PALATE.



13



incisive pad. This papilla corresponds to the anterior palatine fossa, and receives
the terminal filaments of the naso-palatine and anterior palatine nerves^ _Two small
blind recesses, one on either side, are sometimes found upon it. They represent the
lower part of the naso-palatine foramina or canals of Stensen, which in many
animals lead from the mouth into the nose. The transverse rugae, generally about
five or six in number, vary considerably in their development. They are much

Fig. 19. VlEW OF THE SOFT PALATE AND

ISTHMUS FAUCIUM FKOM BEFORE. (-T. S.)

1, soft palate ; 2. its raphe ; 3, uvula ; 4,
anterior, and 5, posterior pillar of fauces ; 6.
tonsil ; 7, posterior wall of pharynx ; 8, dorsuir.
of tongue.

better marked and more regular in the
foetus (Gegenbaur). In the adult the
ridges are often broken up into several
small eminences.

The soft palate (velum pendulum
palati) is formed by a duplication of
mucous membrane, including muscular
fibres and numerous glands. It ex-
tends from the hard palate backwards
and downwards between the nasal and
oral portions of the pharynx, and ends
below in a free border, which in the
middle is prolonged as a conical pro-
cess, the uvula, while at the sides it is
continuous with the posterior pillar of
the fauces. As a rule it is about 10 to
12mm. in thickness, nearly half of
which is due to the glandular tissue
situated between the muscles and the
mucous membrane of the anterior or
under surface of the velum. This
membrane, which is visible from the

mouth, is thinner and redder than that of the hard palate, but like it, is covered
with a scaly stratified epithelium. The median ridge or raphe, which is continued
backwards from the hard palate to the base of the uvula, indicates the original
separation of the palate into two lateral halves. The posterior or upper surface of
the soft palate is convex and continuous in front with the floor of the nasal fossae.
This surface is covered with ciliated columnar epithelium, while on the under aspect
and free margin the epithelium is scaly and stratified.

On both surfaces of the velum are found numerous small compound glands.
They particularly abound on the under surface, where they form almost a complete
layer under the mucous membrane ; they are also very abundant in the uvula.

In the new-born child the whole posterior surface is covered with ciliated epithelium,
but this becomes subsequently replaced by squamous ; the epithelium of the gland-ducts,
however, retains in many instances its ciliated character (Klein).

The muscles of the soft palate are described in Vol. II., Part 2.







14 ORGANS OF DIGESTION.



RECENT LITERATURE OF THE MOUTH, TONGUE, AND PALATE.

Allen, Harrison, The palatal ruga; in man, Proceedings of the Acacl. of Nat. Science of Phila-
delphia, 1888.

Breg-lia. A., Nota anatomica sufla capacitd del cavo buccale, Progresso med., Napoli, 1891.

Fusari, R. et Panasci, A., Demonstration dts terminaisons des ncrfs dans Its glandes
sereuses de la langue dcs mammiferts, Verhandl. des x. internal., inedic. Kongresses, Berlin, ISl'O,
Bd. ii., Abt. i ; Sullc terminazioni nervose nella mucosa e nelle ghiandole sierose dclla lingua dei
mammiferi, Atti della r. accademia delle scienze di Torino, vol. xxv., 1890.

Gaupp. E., Anatomische L'ntersuckungen iiber die Nervenversorgung der Mund- und Nasen-
hbhlendrusen der Wirbeltierc, Morph. Jahrbuch, Bd. xiv., 1888.

Qegenbaur, C., Die Gaumenfalten des Menschen, Morph. Jahvbuch, Bd. iv., 1879 ; Beitrage zur
Morphologic der Zunge, Morph. Jahrbuch, Bd. xi. , 1886 ; Zur Phylogenese der Zunge, Morph.
Jahrb.,Bd. xxi., 1894.

Gillet, H. , Particularity anatomigites du frein de la lewe superieure, Annales de la policlin. de
Paris, 1892.

Gmelm, Zur Morplwl. der Papilla vallata u. foliata, Arch. f. raikr. Anat., Bd. xl. , 1892.

Hintze, K. , Ueb. die Enticickdung der Zunyenpapillen beim Menschen, Inang. Diss., Strassburg,
1890.

His, W., Anatomic menschl. Embryonen. iii., 1885, p. 97 ; Der Tractus tlnjrco-glossus und
seine Beziehungen zuin Zungenbein, Arch, fiir Anatomic, 1891.

Kantliack, A. A.. The Thyreo-glossal duct, Journal of Anatomy and Physiology, vol. xxv, 1891.

Marshall, C. F., Thyro-ylossal duct or " Canal of His," Journal of Anatomy and Physiology,
vol. xxv, 1891.

Merkel, F., Handbuch der topographischen Anatomic, 1 Bd., 1885; Jacolson'sche Organ und
Papilla palatina beim Menschen, Anatom. Hefte, i., 1892.

Podwisotzky, Anatomische Untcrsuchungen iiber die Zungcndrusen des Menschen u. der
Sdugethiere, Inaug. Diss., Dorpat, 1878.

Swain, Die Balgdrusen am Zungengrunde und deren Hypertrophie, Archiv. f. klin. Mecl.,
Bd. xxxix., 1886.

Suzanne, G., Hecherches anatomiques sur le plancher de la bouclie avec etude anntomique et
pathogtniquc sur la grenouillttte commune ou sublinguale, Arch, de Physiol., 1887.

Waldeyer, W., Ueber den harten Gaumen, Corr. Bl. d. anthrop. Ges. (Vers. Ulm, 1892).



THE SALIVARY GLANDS.



15



THE SALIVARY GLANDS.

The saliva, which is poured into the mouth, and there mixed with- the food
during mastication, is secreted by three pairs of glands, named from their respective
situations, parotid, sub-maxillary, and sublingual. Agreeing in their general physical
characters and structure, these glands differ in their size, form, and position.

The Parotid Gland. The parotid (fig. 20, p) is the largest of the three
salivary glands. It lies on the side of the face, in front of the ear, and extends
deeply into the space behind the ramus of the lower jaw. Its weight varies from
five to eight drachms (20 to 30 grammes).

Its outer surface is convex and lobulated, and is covered by the skin and fascia,
and partially by the platysma muscle. It is bounded above by the zygoma, below
by a liue drawn backwards from the lower border of the jaw to the sterno-mastoid

Fig. 20. SKETCH OF A SUPERFICIAL

DISSECTION OF THE FACE, SHOWING
THE POSITION OF THE PAROTID
AND SUBMAXILLARY GLANDS. (Allen



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