336 



DIGESTIVE SYSTEM OF THE HORSE 



from the edge of the dorsum to join the soft palate, forming the anterior pillars of 

 the latter. A central glosso-epiglottic fold (Plica glossoepiglottica) passes from 

 the root to the base of the epiglottis. The mucous membrane presents numerous 

 papillae, which are of four kintls — filiform, fungiform, vallate, and foliate. The 

 filiform papillae (Papillce filiformes) are fine, pointed projections. They cover the 

 upper surface of the body and tip, to which they give a distinct pile. The fungi- 

 form papillae (Papillse fungiformes) are rounded at the free end, which is supported 

 by a neck. They occur principally on the lateral part of the tongue, but are also 

 found scattered over the dorsum and upper surface of the free portion. The 

 vallate papillae (Papillae vallatse) are usually two or three in number. The two 

 constant ones have a diameter of about 7 mm., and are found on the posterior part 

 of the dorsum, one on each side of the median plane, about an inch (ca. 3 cm.) apart. 



Depressor lahii 

 inferioris 



Kera to-h yoideus 



Ilyo-pharyngeus 



Thyroid gland 



Trachea 



T.p. 



Fig. 242. — Muscles of Tongue, Hyoid Bone, Pharynx, etc., of Horse. 

 Ten.ior palati; L. p., levator palati; Pt. p., pterygo-pharyngeu.s; P. p., palato-pharyngeus; S. p., 



stylo-jiharyngeu-*; Th. p., thyro-pharyngeus; C. p., crico-pharyngeus; Th. h., thyro-hyoideus; Hyo. gl., hyo-glos.sus; 

 a. /)., guttural uouch; F. p., foliate papilla; A. v., facial artery and vein. The concealetl parts of the hyoid bone are 

 in licated by dotted line. 



The third, when present, is behind these, is centrally situated, and is always smaller. 

 Rarely a fourth may be seen. They are rounded, broader at their exposed than 

 at their attached surfaces, and are situated in a cup-shaped cavity. The foliate 

 papillae (Papilhe foliatte) are situated just in front of the anterior pillars of the soft 

 palate, where they form a rounded eminence about an inch (ca. 2 to 3 cm.) in length, 

 marked by transverse fissures. The last three varieties are covered with micro- 

 scopic secondary papillse and are furnished with taste-buds. The mucous mem- 

 brane of the root of the tongue presents numerous folds and depressions. Into 

 the latter open the ducts from the lingual glands (Glanduhe linguales), which 

 constitute a thick layer in the loose sul)inu('()us tissu(\ Mucous glands are found 

 also on the dorsum and sides of the tongue. In the submucosa of the root is 

 found also a large quantity of lymph follicles (Folliculi tonsillares) and diffuse 

 lymphoid tissue. 



