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SPLANCHNOLOGY 



in lines parallel with the two rows of the papillae vallatse, excepting at the apex 

 of the organ, where their direction is transverse. Projecting from their apices 

 are numerous filamentous processes, or secondary papillae; these are of a whitish 

 tint, owing to the thickness and density of the epithelium of which they are 

 composed, which has here undergone a peculiar modification, the cells having be- 



Secondary 

 papillae 



Artery 



Vein 



Fia. 1016. A filiform papilla. Magnified 



Artery 

 Vein 



FIG. 1017. Section of a fungiform papilla. Magnified. 



come cornified and elongated into dense, imbricated, brush-like processes. They 

 contain also a number of elastic fibers, which render them firmer and more elastic 

 than the papillae of mucous membrane generally. The larger and longer papillse 

 of this group are sometimes termed papilles conicse. 



FIG. 1018. Semidiagrammatic view of a portion of the mucous membrane of the tongue. Two fungiform papillse 

 are shown. On some of the filiform papillae the epithelial prolongations stand erect, in one they are spread out, and in 

 three they are folded in. 



The papillse simplices are similar to those of the skin, and cover the whole of 

 the mucous membrane of the tongue, as well as the larger papillae. They consist 

 of closely set microscopic elevations of the corium, each containing a capillary 

 loop, covered by a layer of epithelium. 



Muscles of the Tongue. The tongue is divided into lateral halves by a median 

 fibrous septum which extends throughout its entire length and is fixed below to the 



