268 



THE DIGESTIVE SYSTEM 



arranged in the form of an inverted V, the apex being directed 

 toward the larynx. These papillae are much larger than either of 

 the former varieties. They extend slightly above the general level 

 of the epithelial surface, are of an inverted conical shape, and are 

 covered by a smooth layer of stratified epithelium. Their base is 

 surrounded by a deep circular excavation, lined by an invagination 

 A B 



FlG. 225. ClRCUMVALLATE PAPILLAE OF THE HUMAN TONGUE. 



A, axial section ; B, section through the side of a papilla. The serous glands of 

 von Ebner occupy the lower portion of the figure. Hematein and eosin. Photo, x 40. 



of the layer of stratified epithelium, which thus forms a deep 

 trench or vallum about the base of the papilla. 



The epithelium which covers the sides of the circumvallate 

 papillae, as well as that forming the lateral wall of the vallum, con- 

 tains large numbers of taste buds.* The large central connective 



* See Chapter IX. 



