THE TONSILS 



243 



cavities. The lymph nodules which compose the tonsil immediately 

 underlie the epithelial coat, and are embedded in areolar connective 

 tissue. 



The epithelial coat here and there penetrates the substance of the 

 organ in the form of invaginated funnel-shaped depressions, the crypts 

 ('follicles' of the tonsils). The direction of the crypts in the upper third 

 of the tonsil is downward and outward (C. P. Johnson). The ducts of 

 many mucous glands open into the recesses of these branching crypts. 

 The mucus-secreting glands lie in the loose connective tissue which sur- 



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FIG. 248. FROM A CRYPT OF A DOG'S TONSIL. 



a, stratified epithelium ; b, basal margin of the epithelium ; c, infiltration of the epi- 

 thelium by leukocytes; d, spaces in the epithelium filled with leukocytes and epithelial 

 cells; e, blood-vessel; /, lymphoid tissue. X 150. (After Bohm and von Davidoff .) 



rounds the tonsil on all but its faucial surface. The crypts are lined 

 throughout by a layer of stratified epithelium, which is continuous with 

 that on the free surface of the tonsil, but which becomes progressively 

 thinner as it recedes into the deeper recesses of the crypts. 



Many of the lymph cells migrate into the intercellular spaces of the 

 epithelial layer, and even penetrate to the free surface; thus they find 

 their way into the oral cavity, where they are found in large numbers 

 in the saliva, as 'salivary corpuscles' "If such salivary corpuscles are ex- 

 amined in a drop of saliva, freshly prepared, the fine intracellular gran- 

 ules of the polymorphonuclear leukocytes will be seen to undergo an 

 active dancing movement, Brownian motion. The salivary corpuscles are 

 derived not only from the faucial tonsils but from the other lymphoid 

 tissue which is in relation with the oral mucous membrane, e.g., the 

 lingual and pharyngeal tonsils. 



The passage of leukocytes through the epithelial surface of the fauejal 



