THE GUTTURAL POUCHES 879 
tive) is situated on the postero-superior part of the lateral wall of the pharynx, just 
below the level of the posterior nares (Fig. 349). It is a slit, about two inches 
(ca. 5 em.) in length, which slopes downward and backward. It is bounded medi- 
ally by the thin free edge of the tube, from the lower part of which a fold of mucous 
membrane (Plica salpingo-pharyngea) extends in the same direction on the lateral 
wall of the pharynx for a distance of a little more than an inch usually. The outer 
boundary of the opening is the lateral wall of the pharynx. The basis of the tube 
is a plate of fibro-cartilage (Cartilago tube auditivee) which is firmly attached 
dorsally to the fibrous tissue which closes the foramen lacerum, the temporal wing 
of the sphenoid, and the pterygoid bone.! On cross-section the cartilage is seen 
to consist—except at its ends—of two laminze which are continuous with each 
other above (Fig. 348). The medial lamina (Lamina medialis) gradually widens 
toward the pharyngeal end, where it forms a broad valvular flap; this is convex 
medially, and its thin anterior edge forms the basis of the inner margin of the pharyn- 
geal opening. Behind this the lamina has a thick free edge which projects ventrally 
from the roof of the guttural pouch. The lateral lamina (Lamina lateralis) is 
narrow and thin, and is related laterally to the levator and tensor palati muscles, 
which are in part attached to it; it does not extend to the pharyngeal end of the 
tube. The mucous membrane of the tube is continuous behind with that of the 
tympanum and in front with that of the pharynx. On either side it is reflected to 
form a large diverticulum, the guttural pouch. It is covered with ciliated epi- 
thelium, and contains mucous glands and lymph nodules. 
The pharyngeal opening appears to be closed ordinarily. Vermeulen states that it opens 
during deglutition, and that this action is apparently produced by the part of the palato-pharyn- 
geus muscle which is attached to the flap-like expanded part of the tube. 
THE GUTTURAL POUCHES 
The guttural pouches, right and left (Figs. 349, 706), are large mucous sacs, 
each cf which is a ventral diverticulum of the Eustachian tube (Diverticulum 
tube auditivee); they are not present in the domesticated animals other than the 
equide. They are situated between the base of the cranium and the atlas dorsally 
and the pharynx ventrally. Medially they are in apposition in part, but are to 
some extent separated by the intervening ventral straight muscles of the head. 
The anterior end is a small cul-de-sac which lies below the body of the presphenoid, 
between the Eustachian tube and the median recess of the pharynx. The posterior 
end lies near or below the atlantal attachment of the longus colli. The pouch 
is related dorsally to the base of the cranium, the atlanto-occipital joint capsule, 
and the ventral straight muscles. Ventrally it lies on the pharynx and the origin 
of the esophagus. Laterally the relations are numerous and complex. They 
comprise the pterygoid, levator palati, tensor palati, stylo-hyoideus, occipito- 
hyoideus, occipito-mandibularis, and digastricus muscles; the parotid and mandib- 
ular salivary glands; the external carotid, internal maxillary, and external maxil- 
lary arteries; the internal maxillary and jugular veins; the pharyngeal lymph 
glands; the glosso-pharyngeal, hypoglossal, and anterior laryngeal nerves. The 
vagus, accessory, and sympathetic nerves, the anterior cervical ganglion, the in- 
ternal carotid artery, and the ventral cerebral vein are situated in a fold of the 
dorsal part of the pouch. The pouch is reflected around the dorsal border of the 
great cornu of the hyoid bone so as to clothe both surfaces of the dorsal part of the 
latter. It thus forms an outer compartment, which extends backward lateral to 
| the great cornu and the occipito-hyoideus muscle; this compartment is related 
laterally to the parotid gland, the articulation of the jaw, the ascending part of the 
internal maxillary artery, the superficial temporal artery, and the facial nerve; dor- 
1 There is, strictly speaking, no osseous part of the tube such as occurs in man. In the horse 
the cartilage extends to the tympanic orifice. 
