DIGESTIVE SYSTEM. 



181 



connective-tissue fibers is also present in the sub- 

 mucosa. The submucosa is therefore capable of 

 being greatly distended, as is the case in throat in- 

 fections, such as diphtheria, where the congestion 

 is so great as to interfere with respiration. The 

 diphtheria germs and toxins are thus lifted up and 

 walled off from the deeper structures and normal 



\. Epithelium. 



Crypt. 



Lymphoid nodules. 



Tonsillar sinus. 



Fig. 132. Section through the pharyngeal tonsil of man (Sobotta). 



blood supply. This is nature's method of eliminat- 

 ing the disease, with the possible danger to the pa- 

 tient of suffocation. 



External to the submucosa come several layers of 

 striated muscle fibers forming the pharyngeal muscle, 

 the description of which belongs to gross anatomy. 



Tonsil. The tonsils are two oval lymphoid 

 masses imbedded in the lateral walls of the pharynx, 



