1110 



DIGESTIVE SYSTEM 



to the foliate papillae (i. e., in the regions of the taste-buds), the mucous glands are displaced by 

 the serous glands (of von Ebner), which have a watery secretion (fig. 860). Finally, on the 

 inferior surface of the tongue, on either side of the frenulum near the apex, are the anterior 

 lingual glands (glands of Nuhn or Blandin). Each is about 15 mm. in length, and is composed 

 of a group of racemose glands with three or four very small ducts opening on the surface of the 

 tongue near the pHca fimbriata. The anterior lingual glands are deeply placed and are covered 

 not only by the mucosa, but also by some of the longitudinal muscle fibres (inferior longitudinal 

 and styloglossus). This gland is of the mixed type, though chiefly mucous. 



Fig. 859. — From a Section of the Lingual Tonsil of an Adult Man. X 20. 1. Pit 

 containing leucocytes which have infiltrated its epithelium on the left side; that on the right is 

 almost intact. (Lewis and Stohr.) 



Median section of a nodule 



Diffuse lumphoid tissue ^ 



Lymph nodules 



Duct of a mucous gland 



J Epithelium 



Periphery of a nodule 



I I Tunica propria 

 Fibrous capsule 



Blood vessel 



Muscles of the tongue. — A layer of fibrous connective tissue, the linguafseptum, separates 

 the halves of the tongue, extending in the median plane from the apex to the root, where it is 

 attached below to the hyoid bone. The muscles of the tongue are classified as extrinsic and 

 intrinsic. The extrinsic muscles (fig. 855) extend into the tongue from without. They are 

 the hyoglossus, chondroglossus, genioglossus, styloglossus, and glossopalatinus (palatoglossus), 

 all of which are described elsewhere (see Section IV.) 



Fig. 860. — Diagram of the Distribution of the Lingual Glands. Horizontal lines 

 indicate the mucous type;_^cross-hatched, the mixed type; and dotted areas, the serous type. 

 (After Oppel.) 



The intrinsic muscles. — The longitudinalis superior (fig. 861) is a superficial longitudinal 

 stratum extending from the base to th(; apex of the tongue, immediately beneath the mucosa 

 of the dorsum, to which many of its fibres are attached. The longitudinalis inferior (fig. 861) 

 is composed of two muscle-bands extending from base to apex on the inferior surface of the 

 tongue, and is situated between the hyoglossus and the gcnioglos-sus, some of its fibres near 

 the apex mixing witii the styloglossus, while dorsally some are attached to the hyoid bone. The 

 transversus linguae (fig. 861) consists of fibres which pass transversely, and is situated between 



