PHARYNX. 
related to the internal carotid artery, which 
vessel will be applied to its outer side and be- 
hind it, so that when an opening is required in 
the tonsil, the point of the lancet should be 
directed inwards towards the cavity of the 
mouth. The tonsils and soft palate are well 
supplied with blood by the palatine and ton- 
sillitic branches from the facial, by the ascend- 
ing pharyngeal and internal maxillary arteries. 
A considerable plexus of veins is formed round 
the tonsil, which terminates in the pharyngeal 
venous plexus. Besides the nervous twigs de- 
rived from the palatine branches of Meckel’s 
ganglion, the soft palate also receives filaments 
from a plexus formed around the tonsils by the 
tonsillitic branches of the glosso-pharyngeal, 
which has been called the circulus tonsillaris. 
For the description of the tongue, the remaining 
boundary of the cavity of the mouth, see 
ToncuE. 
Course of the mucous membrane.—The mu- 
cous membrane of the mouth is continuous 
with that of the pharynx and larynx. Com- 
mencing with the gums anteriorly, it passes 
upon the exterior surfaces of the upper and 
lower maxillary bones, and from thence is re- 
flected on the cheeks laterally and upon the 
inner surface of the lips anteriorly, forming a 
small fold in the median line, called the frenum, 
to each ; it invests the free borders of the lips 
and becomes continuous with the skin at a well 
defined line of demarcation. When the jaws 
and teeth are closed, the cheeks and lips are 
naturally in apposition with them ; but if sepa- 
rated by distending the cheeks, the mucous 
membrane we have been tracing will be seen 
to line an anterior or second buccal cavity form- 
ing a kind of antechamber to the interior of the 
mouth. Proceeding from the gums posteriorly 
the membrane descends upon the interior of 
the lower jaw to be reflected upwards to the 
under surface of the tongue, and forms for it 
anteriorly and in the median line a prominent 
fold, the frenum lingue; this occasionally is 
prolonged forwards to the apex of the tongue, 
interfering with its movements in the act of 
sucking: a slight division of the frenum under 
these circumstances is all that is required. From 
the under surface of the tongue the mucous 
membrane invests that organ and is continued 
from its base to the epiglottis, and after forming 
three folds, called glosso-epiglottic, is reflected 
over its free edge to be continuous with the 
laryngeal membrane. From the gums of the 
upper jaw posteriorly it invests the hard and 
soft palate and passes round the posterior free 
border of the latter, after enclosing the uvula, 
to cover its nasal surface. From the cheeks 
laterally it is to be traced over the anterior 
’ pillars of the fauces, the internal surface of the 
tonsils dipping into its mucous crypts, and 
lastly forming the folds of the posterior pillars 
is continuous with the mucous membrane of 
the pharynx. Throughout the cavity of the 
mouth it is invested with epithelial scales, and 
its submucous areolar tissue is remarkably in- 
creased in thickness and density when forming 
the gums and palate. 
953 
Function.—The pharynx, mouth, and palate 
are most obviously associated in the process of 
deglutition, in-;which we may trace three suc- 
cessive stages: in the first, the food after being 
reduced to a softened pulp by mastication and 
admixture with the saliva is conveyed to the 
back part of the mouth by the movements of 
the tongue against the hard palate; this is a 
purely voluntary act and can be arrested at the 
will of the individual: the food carried past 
the anterior arch of the fauces, the second act 
of deglutition immediately succeeds ; this in- 
volves the consentient action of numerous mus- 
cles and isa most complicated process. If the 
movements of the velum palati and the poste- 
rior pillars of the fauces are examined during 
an effort to swallow, the former is perceived to 
become somewhat more arched towards the 
cavity ofthe mouth and to be rendered tense, 
but it appears to maintain nearly its naturally 
oblique direction. It has been supposed that 
the velum is raised during deglutition, in order 
to prevent the food from passing to the nose, 
but this opinion is now generally considered 
erroneous. Miiller says, “ Most writers incor- 
rectly state that during deglutition the food is 
prevented from entering the posterior nares by 
the soft palate being raised, a movement which, 
if performed, could not in any case completely 
cut off the pharynx from the posterior nares.” 
With the stretching of the velum the posterior 
pillars or palato-pharyngei muscles will be 
seen to approach each other, particularly above, 
so as to reduce the isthmus faucium toa narrow 
triangular slit, broadest below. If the food is 
now pressed backwards by the tongue, it will 
be urged through this dilatable chink in a 
direction downwards and backwards, occasioned 
partly by the oblique resisting surface of the 
velum, and partly by the wider aperture left 
between the posterior pillars inferiorly, perhaps 
also by their greater disposition to yield in 
that direction to the pressure of the food as it 
passes between them; meanwhile the pharynx 
(and the larynx with it) has been drawn up- 
wards, and at the same time widened by the 
action of the stylo-pharyngei muscles, to receive 
the morsel, which in passing into it presses the 
epiglottis down upon thesuperior apertureof the 
larynx, and gliding over it is then immediately 
carried on to the esophagus by the action of 
the constrictor muscles. The epiglottis in 
being shut down upon the opening of the 
larynx protects the respiratory tube, but it is 
not absolutely essential for that purpose; ex- 
periments have been performed on animals 
where the epiglottis has been removed, and it 
has been destroyed by disease in the human 
subject without any material difference evi- 
denced in deglutition, the action of the laryngeal 
muscles closing the aperture of the larynx. 
This second act of deglutition may be performed 
at will though only the saliva is swallowed, 
but the effort soon becomes fatiguing. When 
the food, however, has reached beyond a cer- 
tain limit in the mouth, no effort on our part 
can prevent deglutition from taking place. (For 
the influence of the nerves upon this function 
