DIGESTIVE SYSTEM. 



175 



the obliterated thyroid duct. The dorsal surface is 

 studded with three sets of papillae, to be described in 

 detail. 



Papillae. i. Filiform Papillae. These are not 

 only the smallest but by far the most numerous, and 

 give the tongue a velvety appearance. They are 

 arranged in divergent rows that extend outward and 

 forward from the median sulcus. Each papilla is 

 conical, points backward, and is covered by a thick 



Fig. 126. Section through two filiform papillae of tongue. 



layer of stratified, horny, squamous epithelium. 

 The function of these papillae is purely prehensile. 

 In carnivorous animals they give the tongue a rasp- 

 like structure that serves effectually in cleaning 

 bones. It is said that a tiger, in this way, can draw 

 blood from a living hand. 



2. Fungiform Papilla. These are less numerous, 

 larger, and supplied with blood, which gives them a 



