i6oo 



HTM AN ANATOMY. 



FIG. 1355. 



Muscular 

 fibres 



geal tonsil in the upper part of the pharynx, the tubal tonsils at the openings of 

 the Eustachian tubes, especially on the posterior fold, and the lingual tonsil, con- 

 sisting of the scattered adenoid collections 

 over the posterior third of the tongue. Many 

 additional lymph-nodules are scattered over 

 the sides and roof, so connected as to form 

 a lymphoid ring at the upper part of the 

 pharynx. 



The faucial tonsils (Figs. 1326, 1353) 

 are theoretically two almond-shaped masses 

 of adenoid tissue, placed one on each side of 

 the oro-pharynx, between the pillars of the 

 fauces. The long diameter is vertical, and 

 they have an outer and an inner surface and 

 an anterior and a posterior border. The 

 length is conventionally put at from 2025 

 mm., the breadth at 15 mm., and the thick- 

 ness at 10 mm. Practically, however, there 

 is no definite shape nor size. In childhood 

 the tonsil generally projects as a globular 

 mass. If it extends more than slightly be- 

 yond the level of the faucial pillars, it is said 

 to be enlarged. After middle life it rises usu- 

 ally but little from the floor of the niche. 

 The shape of the free surface gives no clue 

 to the size of the deep surface. In structure 

 the tonsil is a mass of adenoid tissue en- 

 closed in a fibrous capsule which is crossed 

 on both the deep and free surfaces by a thin 

 layer of muscular fibres. The superficial layer 

 belongs to the palato-glossus ; the deep or 

 external layer arises from the superior con- 

 strictor and passes to the tongue. Beyond 

 this externally are fat and areolar tissue. The closely adherent mucous membrane 

 covers the free surface, which is full of pits from i or 2 mm. to i cm. in depth. 



The larger ones often expand be- 



FIG. 1356. j ow t h e orifice, so that they may 



collect and retain secretions. A 

 small free space, the snpratonsillctr 

 fossa, lies above the tonsil at the 

 apex of the niche containing it ; at 

 the front of this there is very often 

 a series of crypts with detached 

 adenoid tissue about them, bur- 

 rowing under the anterior pillar 

 from behind and making a pouch 

 beneath a fold, the plica trian- 

 gular is. The adenoid tissue is 

 continuous below with that of the 

 tongue. The mucous membrane 

 of the oro-pharynx shows many 

 si altered lymphoid follicles in its 

 walls, especially on the sides at 

 and above the level of the tonsils. 

 Vessels. The arteries sup- 

 plying the faucial tonsil are de- 

 rived from several source*, and the arrangement of the vessels is extremely irregular ; 

 the branch from the ascending pharyngral and that from the facial artery one or 

 both enter its base, while twigs from the lingual and descending palatine arteries, 



Section through faucial tonsil, showing general dis- 

 position of lymphoid tissue. X 20. 



. ' * 

 J' &&&** 



Lymphocytes, 

 invading 



.Epithelium 



.Blood-vessel 



. Lymphoid 

 tissue 



v 



. 



'- 



Portion of faucial tonsil, showitu; t-pitli.-lial lining of crypt invaded 

 by esr;iping Kmplioi vies. X 325. 



