228 THE DIGESTIVE SYSTEM 



The palatine tonsil is formed by the outgrowth of numerous 

 little diverticula from the pharyngeal wall. These diverticula 

 become surrounded by a mass of lymphoid tissue, which 

 rapidly increases in amount and bulges the mucous membrane 

 inwards. An ill-defined capsule of fibrous tissue covers the 

 tonsil on its lateral aspect. The original diverticula remain 

 patent and form the tonsillar crypts, which become filled with 

 a caseous exudate in follicular tonsillitis. The crypts of the 

 tonsil provide access to many varieties of micro-organisms, of 

 which the tubercle bacillus is much the commonest. During 

 the early years of life, the lymphoid tissue of the palatine 

 tonsils may hypertrophy to such an extent that they almost 

 meet in the middle line, and this condition is usually accom- 

 panied by a similar hypertrophy of the pharyngeal tonsil 

 (p. 329). The respiratory difficulties caused by this enlarge- 

 ment may be so great that the contour of the chest is greatly 

 altered, pigeon-chest, Harrison's sulcus and other deformities 

 being induced. 



The lymph vessels of the palatine tonsil pass to one of 

 the upper deep cervical glands, placed in close relation with 

 the internal jugular vein at the level of the greater cornu of the 

 hyoid bone. From this lymph gland efTerents pass to the lower 

 group, some of which are intimately related to the cervical 

 dome of the pleura. It has been suggested (p. 352) that 

 tuberculous infection of the palatine tonsil may, through the 

 medium of the lymph glands and vessels, be responsible for 

 the production of apical phthisis. Other efferents descend 

 into the thorax and establish connexions with the bronchial 

 glands. In this way another route is opened up for the 

 passage of tuberculous infection from the palatine tonsil to the 

 lung. 



The posterior wall of the oral part of the pharynx is a 

 common site of angio-neurotic cedema> a circumstance which is 

 accounted for by the laxity of the submucous tissue in this 

 situation. 



The muscular wall of the pharynx is entirely deficient 



