THE GITTTURAL POUCHES 879 



tivse) 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 cm.) 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 (Cartilage tubae auditivse) 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 laminae 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 iimer 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 of which is a ventral diverticulum of the Eustachian tube (Diverticulum 

 tubae auditivse) ; they are not present in the domesticated animals other than the 

 equidse. 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 hes 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 oesophagus. 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 sahvary 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 comu 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 comu 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. 



