THE LYMPH NODULES 



123 



beneath the n()ii-])a])illiate(l e])itheHiiiii of the ui)i)er surface of the 

 tongue posterior to the foramen cecum. Another group, composhig 

 the pharyngeal tonsil, hes just below the epithehum in the upper 

 posterior face of the pharynx near the entrance of the nasal passages. 

 Similar masses of lymphoid tissue at the entrance of each Eustachian 

 tube form the tubal tonsils. In all these structures, groups of 

 nodules lie below a stratified epithelial membrane. (Fig. 72.) 

 Scattered crypts, or pits, may occm- in the epithelium and 

 extend down into the tonsil tissue. These crypts are lined with 

 stratified squamous ei)ithelium which rests upon a stroma of 



Fig. 72.— Tonsil of the dog. The nodules are closely packed below a stratified 



squamous epithelium. 



fibroelastic connective tissue continuous with similar tissue forming 

 the coarse framework for the nodules. The lymph nodules are 

 sometimes clearly separated, but may ha\'e diffuse lymphoid tissue 

 connecting them. A fine netw^ork of reticular connective tissue 

 extends through the nodules and between them. Below the 

 lymphoid mass is a dense fibroelastic connective tissue which merges 

 with similar tissue associated with the skeletal muscles of the neck. 

 Tonsil tissue gives rise to a supply of lymphocytes, many of which 

 may be lost by passing through the epithelial membrane; others 

 may enter capillaries associated with the reticulum. The tonsils 

 commonly atro])hy but may become hy])ertrophied under conditions 

 of infection. Their removal is often followed by regeneration of 

 lymphoid tissue in the same locality. 



