; MERE, SPEC ACE NX. 983 
The chamber of the naso- pharynx is irregular in shape, and is enclosed by siz 
walls—namely, anterior, posterior, two lateral, and a floor—together with a roof or 
vault formed above by the approximation of the anterior and “posterior walls. 
The anterior wall, which slopes upwards and backwards, is entirely occupied by 
the two posterior nares, with the nasal septum between them (Fi ig. 660). 
The posterior wall is inclined upwards and forwards, and forms the vault of the 
pharynx (fornix pharyngis) above by meeting the anterior wall at a rounded angle. 
On the upper part of the posterior wall, at and above the level of the Eustachian 
orifices, there is seen, particularly in early life, a considerable accumulation of 
ly mphoid tissue, associated with a thickened and folded condition of the mucous 
membrane in fhe child. This is the pharyngeal tonsil (tonsilla pharyngea, 
Figs. 661 and 662). In old age it becomes very indistinct, or completely disappears ; 
whilst in the child it is often increased in size, and occasionally, when greatly 
hypertrophied, blocks up the naso-pharynx almost completely. 
In connexion with the lower part of the pharyngeal tonsil, there is found, constantly 
in the child and occasionally in the adult, a small median recess which runs upwards and 
backwards in the wall of the pharynx for some distance, and is known as the bursa 
pharyngea (lig. 661). 
Three leading views are held as to the nature of the bursa pharyngea, namely— 
1. That it is the remains of Rathke’s pouch, from which the anterior lobe of the pituitary 
body is formed, 2. That it is a crypt connected with the formation of the pharyngeal 
tonsil. 3. That it is an independent outgrowth of the mucous membrane. The last view 
is perhaps most generally accepted. 
The floor of the naso-pharynx is formed by the upper surface of the soft palate 
(Fig. 661), which in its anterior part is a direct continuation backwards of the floor 
of the nasal cavity, whilst posteriorly it slopes strongly downwards and backwards. 
Between the floor and the posterior wall is left the aperture referred to above as 
the pharyngeal isthmus, through which the naso-pharynx communicates with the 
rest of the ph iaryngeal cavity. By the action of the palatal muscles the floor can 
be raised or depressed, and these changes of position are accompanied by corre- 
sponding alterations in the size and shape of the cavity. 
Each lateral wall of the naso-pharynx (Fig. 661) is occupied in the greater part 
of its extent by the opening of the Eustachian tube, behind which is seen a 
vertical slit-like depression leading into a recess, the lateral recess of the pharynx, 
or fossa of Rosenmiiller. 
The pharyngeal orifice of the Eustachian tube (ostium pharyngeum) is a con- 
siderable opening, usually of a somewhat triangular form, with a characteristic 
infundibular or fumnel-like appearance (Fig. 661). It is bounded above and behind 
by a prominent rounded ridge, the Eustachian cushion (torus tuberius). This 
ridge is due to the projection of the cartilage, which surrounds the Eustachian 
passage above and behind, but is absence below and in front. The prominence 
of the posterior, as contrasted with the anterior margin of the orifice, and the 
direction of the tube itself, which runs strongly forwards as well as inwards 
(traced from the tympanum), greatly facilitate the introduction of a Eustachian 
catheter. 
The exact position of the orifice is of importance in connection with this latter 
operation. It is situated on the side-wall of the naso-pharynx, a short distance 
(about 4 to } inch) behind the posterior end of the inferior turbinated hone, and 
immediately above the level of the hard palate (Figs. 661 and 662). 
A slight ridge of the mucous membrane descends from the lower end of the Eustachian 
cushion on the side-wall of the pharynx, and gradually becomes lost. This is known as 
the salpingo-pharyngeal fold (plica salpingo-pharyngea). Another less developed ridge, 
the salpingo-palatine fold (plica salpingo-palatina), passes from the anterior border of 
the Eustachian orifice downwards and forwards to join the palate. In front of the latter 
lies an indistinet groove, the naso-pharyngeal groove, which indicates the separation of 
the nasal cavity from the naso-pharynx. 
The levator palati muscle in descending runs parallel to the Eustachian tube, and along 
its lower border. As it enters the palate, it produces, particularly when in a state of 
