880 THE SENSE ORGANS AND SKIN OF THE HORSE 
sally it covers the mandibular nerve and its chief branches, and is attached to the 
styloid process of the conchal cartilage. 
Each pouch communicates with the pharynx through the pharyngeal orifice 
of the Eustachian tube, and is in direct continuity with the mucous membrane of 
the latter. 
The average capacity of each pouch is about ten fluidounces (ca. 300 ¢.c.); of 
this, the lateral compartment is about one-third. 
Temporal muscle 
Scutiform cartilage, 
posterior process 
Conchal cartilage 
Brachiocephalicus 
tendon 
Nerves IX, X, XT 
Ventral cerebral vein 
Internal carotid artery 
Guttural pouch 
Occipito-hyoideus 
muscle 
Jugular vein 
Int. maxillary artery 
Ext. maxillary artery 
Parapharyngeal lymph 
glands 
Occipito-mandibularis 
muscle 
Sterno-cephalicus tendon 
Mandibular gland 
Thyroid cartilage 
Ext. maxillary vein 
Omo-hyoidei + sterno-hyoidet 
Fic. 706.—Cross-sectTion oF Heap or Horse. 
The section passes through the base of the external ear and just behind the posterior border of the mandible. 1, 
Rectus capitis ventralis minor; 2, rectus capitis ventralis major; 3, medial walls of guttural pouches in apposition; 
4, 4, arytenoid cartilage, upper piece being apex; 5, posterior pillar of soft palate; 6, false vocal cord; 7, lateral ventricle 
of larynx; 8, true vocal cord; 9, vocal muscle; 10, thyro-hyoideus muscle. The cavity in which the number 4 is placed 
is the pharynx, which was left unmarked by an oversight. 
The pouch is a delicate mucous membrane which is in general rather loosely 
attached to the surrounding structures. It is lined with ciliated epithelium and is 
supplied with glands which are chiefly mucous in type. 
It is worthy of note that the pharyngeal orifice of the Eustachian tube is at such a level as 
to provide (in the ordinary position of the head) only an overflow outlet for the escape of fluid 
which may accumulate in the pouch. The expanded part of the tube forms with the wall of the 
pharynx a sort of vestibule, at the posterior part of which is the opening of the guttural pouch. 
