392 



DIGESTIVE SYSTEM OF THE HORSE 



The latter are marked by crjrpts and consist essentially of a mass of lymphoid 

 tissue; they are known as lingual follicles (FoUiculi linguales), and taken together 

 form what is sometimes called the lingual tonsil. The lingual glands (Glandulse 

 linguales) constitute a thick layer in the loose submucous tissue and also lie between 

 the muscle bundles. Mucous glands are found also in part of the dorsum and sides 

 of the tongue. 



The lingual muscles (Mm. linguse) may be divided into intrinsic and extrinsic. 

 The intrinsic musculature consists, not of distinct muscles, but rather of systems 

 of fibers which run longitudinally, vertically, and transversely, blending with the 

 extrinsic muscles, which are now to be described.^ 



Genio-glossus 

 Depressor labii 



Thyroid Trachea 

 gland 



inferioris 



Fig. 332. 

 T. p., Tensor palati; L. 



-Muscles of Toxgue, Hyoid Bone, Pharynx, etc., 



OF Horse. 

 p., levator palati; PI, p., pterygo-pharyngeus; P. p., palato-pharyngeus; S. p., stylo- 

 pharyngeus; Th. p., thyro-pharyngeus; C. p., crieo-phar.\'ngeus: Th. h., thyro-hyoideus; Hyo. gl., hyo-glossus; G. p., 

 guttural pouch: F. p., foliate papilla; .4. v., facial artery and vein. Most of the left ramus of the mandible is removed. 

 The concealed parts of the hyoid bone are indicated by dotted lines. 



1. Stylo-glossus. — This is a long, thin muscle, which lies along the lateral part 

 of the tongue. It arises by a thin tendon from the lateral surface of the great 

 cornu of the hyoid bone, near the articulation with the small cornu. It terminates 

 near the tip of the tongue by blending with its fellow of the opposite side and with 

 the intrinsic musculature. The action is to retract the tongue. Unilateral con- 

 traction would also draw the tongue toward the side of the muscle acting. 



A small muscular band sometimes arises on the thyroid cornu of the hyoid bone and ends 

 on the tendon of origin of the stylo-glossus. In some cases a similar band arises higher up, with 

 and on the hyo-glossus. 



2. Hyo-glossus. — This is a wide, flat muscle, somewhat thicker than the pre- 



1 This distinction is more or less conventional. It is evident that much of what may appear 

 on cross-sections of the tongue to be intrinsic muscle is in reality a part of the extrinsic musculature. 

 The arrangement is further complicated by the existence of bundles running in various directions,, 

 intercrossing of bundles, and the breaking up of the systems by masses of fat. 



