DEGLUTITION, 
Pie nae with the bag of the pharynx. The general 
direGtion of the cavity, in the ereét pofition of the body, is 
ho onl: deny e former opening placed direQly for- 
er aelas rds. 
e of the palate is terminated on its an- 
terior and lateral a cea: by the alveolar portion of the uppe 
jaw, containing the upper feries of teeth. The pace 
ing part of the inferior maxillary bone, with the lower teeth, 
projects into the mouth below. When the cavity is fhut, 
the two rows of teeth meet together, ye divide it into two 
parts having no communication with each other; vz: an 
outer or front bap ar fituated between ce lips and nie 
on one fide ee uter E aeuad ‘of the teeth and t 
fockets on ne other ; and a or 
the fpace left within ie aches laclenibe 
the open ftate of the mouth thefe two divifions communicate 
by the wide aperture left between the two rows of the teeth. 
The extent of the cavity of the mouth differs in its dif- 
ferent directions. When it is fhut, the fuperior furface of 
When the procefs of maftication is going on, the tongue and 
jaw defcend, and the lips and cheeks are di tlended with the 
; thus the cavity is increafed in all its dimenfions. The 
meter, which in he vielen ftate of parts 
and more confiderable 
in proportion to the depreffion eielcee: aw. e mea- 
{ure from fide to fide, in the firft-mentioned ftate, is os dif- 
tance between the outer edges of the teeth on each fide; and 
that from before backwards is nearly the fame as the laft. 
Both thefe diameters will be affeted confiderably by the 
motions of the lips and cheeks, and will = oa or {maller, 
according to the diltenfion of thofe organ 
e cavity of the mouth is lined a a foft and vafcular 
embrane, continuous at th perture wit 
common integuments of the face; extended behind into the 
harynx ; and differently organized in different parts 8 
courfe. Fi he loofe and tumid 
Tt then 
see saraaar are name Afcending 
over the outer alveolar fa it approaches the necks of the 
teeth, cae a greater firmnefs of texture, and forms the 
ums. On the aivedlee edges of the maxillary bones, and, 
gum, the membrane is perforated by a n 
equal to that of the teeth ; , and it adheres dlotely iy es 
eckso 
is *alfo conneéted with the periofteum that lines the “heeali 
It is then continued over the internal alveolar lamina of 
both jaws; affords a covering above to the bony palate; 
and is prolonged over the under furface of the foft palate, 
at the pofterior or loofe edge of which it becomes conti- 
nuous with the pituitary membrane of the nofe. From the 
cheek it goes over the ramus of the jaw, and is continued 
with the membranous fold that paffes from the foft palate 
to the tongue. After covering the inner alveolar plate of 
the lower jaw, it ioe to the under —— and ei and 
then to th of the tong ppofite to-the 
fymphyfis of the b d juft ov Se mre ee of the 
brane is produced loofely from the bone to the tongues 
nd it covers on each fide towards the front a {mall oblon 
eminence, fe 
vary gland. From the Lies of the tongue the membrane 
fs fat, and numerous glare 
ende th 
Sana us and 5 
wo rows of t an. and attached below to the whole 
length of the eee portion of the lower jaw ; and poffeff- 
ing a middle tranfverfe fiffure, parallel to the teeth, and core 
re{ponding to the interval of the two rows, but much fhorter 
than that interval ;—c — the fis and cheeks. 
The Jips are the two moveable portions of the above-de- 
{cribed produdtion, nner Gen the front teeth, Prva 
the mouth at its anterior part, and forming, by t rred 
and feat facing edges, the margins of the « opening a the 
mouth. The upper lip are the part ] 
that opening and t fe: the low 
ees the oan orifice and a Jower j aw. 
very important, from the influence which they exert on 
ie general a rclicn of the countenance, not to mention 
their fhare in articulation, maftication, &c. They are 
united at the two corners of the m by acute anglee, 
named their commiffures. Thefe are aay mufcular; fo 
a they admit of confidcrable extenfion and retraction: 
Their loofe edge, which is their thickeft part, and i is marked 
by feveral lines croffing between the two margins, is the 
point of continuity aay the mucous membrane of the 
mouth, and the mon integuments. 
The external flratum of the tins confifts of fin oa 
ell as for ~ hae which grow 
at characteriltic “af. 
the corner of the mouth above, the Reece Leas 
and depreffor anguli oris at the commiflure, the de- 
preffors of ao lower lip below. The mufcular layer is fol- 
lowed by a confiderable number of large, rounded, mucous 
glands ae labiales), arranged in an uniform ftratum, 
e¢ mouth by m 
in general: it is 
and deep ved from minute injections ; ; its furface is moiftened. 
the m The 
red {welling part, which forms the very opening of the 
mouth, is ditinguithed fromthe common fkin, external: el bya 
clearly defined line, and from the mucous membrane on the 
infide. It is this part which forms, by its clea sey aa 
rednefs, fo beautiful a contraft with the pearly whitenefs of 
the teeth. It poffeffes cuticles, which often feparate in 
dry and ragged gaya aejaiiaele in cold weather. The 
cutis at = ae is furn with numerous villi, indicating 
ca 
te 
d 
conftantly ce fame thicknefs.: which is not more favourable 
