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986 THE DIGESTIVE SYSTEM. 
The ascending palatine artery, running upwards and backwards between the stylo- 
glossus and stylo-pharyngeus, lies in close relation to the outer surface of the tonsil— 
separated only by its capsule and the superior constrictor—as does also the tonsillar 
artery, which is often represented by a branch of the last. More external still lies the 
internal pterygoid and the ramus of the jaw; whilst the imternal carotid artery, 
with the large cranial nerve trunks, is placed # to 1 inch behind and to its outer side 
(Fig. 664). 
The size of the tonsils is extremely variable, but as a rule, in early life, they 
measure something under 1 inch (20 to 22 mm.) from above downwards, about # inch 
(18 to 20 mm.) antero-posteriorly, and 4 inch (12 to 15 mm.) from within out. 
In the child and young adult there is usually seen a thin triangular fold of mucous mem- 
brane, the plica triangularis (His), which stretches from the anterior palatine arch backwards for 
a variable distance over the tonsil (Fig. 661). Its apex is directed upwards towards the soft 
palate, its base towards the tongue, and its free margin crosses the tonsil, to which it often 
adheres in later life. In this latter condition the plica encloses a more or less distinct space 
situated between itself and the tonsil, in which diseased processes are often set up. 
Above the tonsil, as already mentioned, is found a variably-developed depression, the supra- 
tonsillar fossa, which occasionally is of considerable size, and then extends either upwards into 
the soft palate or forwards and downwards beneath the plica triangularis. This fossa is frequently 
the seat of suppurative changes, and is consequently of considerable clinical importance. 
The supratonsillar fossa, like the lateral recess of the pharynx, is the remains of the pharyn- 
geal portion of the second visceral cleft. The palate in its growth backwards crosses the cleft, 
which it divides into two parts—namely, the pharyngeal recess above, and the supratonsillar 
recess below the soft palate. 
In the severe heemorrhage which has been known to follow excision of an enlarged tonsil, 
and which has been erroneously attributed to the wounding of the internal carotid artery, the 
blood is derived chiefly from enlarged branches of the ascending palatine, tonsillar, or ascending 
pharyngeal vessels. 
The arteries of the tonsil are derived from the ascending palatine and tonsillar branches of 
the facial, the ascending pharyngeal of the external carotid, and the dorsalis lingue of the 
lingual. The veins pass to the tonsillar plexus, on the outer side of the tonsil, which is an 
offshoot of the pharyngeal venous plexus. 
Nerves.—The tonsil receives a special branch from the glosso-pharyngeal ; this unites with 
branches from the pharyngeal plexus in a small plexus tonsillaris which supplies the organ. 
The lymphatics are extremely numerous, and pass down to join some of the submaxillary 
lymphatic glands near the angle of the jaw. 
Laryngeal Portion of the Pharynx (pars laryngea).— This division of the 
pharyngeal cavity lies behind the larynx (Fig. 660). It is wide above, where 
it is continuous with the oral portion, and maintains a considerable width until 
within about an inch of its termination, when behind the cricoid cartilage it 
narrows rapidly and passes down to join the cesophagus. Except during the 
passage of food, the anterior and posterior walls of this latter part are in contact, 
and its cavity is reduced to a mere transverse slit (Fig. 661). 
The anterior wall of the laryngeal portion of the pharynx is formed in its 
whole extent by the back of the larynx, of which the following parts are seen 
within the pharyngeal cavity (Fig. 660):—The epiglottis above; below this the 
superior aperture of the larynx, bounded at the sides by the aryteno-epiglottic 
folds; outside these folds is seen on each side a deep recess, the sinus pyriformis 
(recessus piriformis, Fig. 660). Lower down still, the back of the arytenoid and 
cricoid cartilage, covered by muscles and mucous membrane, are visible. 
Its posterior and lateral walls are directly continuous with the corresponding 
walls of the oral pharynx, and present no features which require special notice. 
A prominent fold of the mucous membrane, extending from the side of the epiglottis, runs 
up along the lateral wall, upon which it ends near the posterior palatine arch. This, the 
pharyngo-epiglottic fold, is often described as a lateral glosso-epiglottic fold. 
The sinus pyriformis is a deep depression, seen on each side between the aryteno- 
epiglottic fold and the ala of the thyroid cartilage. When viewed from above, as 
in laryngoscopic examinations, it appears of a pyriform shape, the wider end being 
directed upwards and forwards. When viewed from behind, the recess 1s boat- 
shaped and elongated in the vertical direction. Its outer wall is formed by the 
thyroid cartilage and thyro-hyoid membrane, covered by mucous membrane ; its 
