2 7 3 



DIGESTIVE ORGANS. 



[sect. 131. 



smooth, or, perhaps, only more or less broken by cracks. 4. The epithelial 

 processes of the filiform papilla are beset with fungi {Leptothrix buccalis, 

 ltobin). Every microscopist is, probably, acquainted with brownish elongated 

 (0-12'" to o'2+'" long, 0-04'" to 0-08'" broad) bodies (fig. 122) occurring on the 



Fig. lift. 



/// 



A collection of epithelial cells, a. covered by the granular matrix of the fungus, 6, from 

 which luxuriantly growing fungi (c) proceed. Magnified 350 times, from man. 



coat of the tongue, and which consist of a dark axis and of a finely granular 

 cortex. It is only the central part of this structure which is composed of 

 confined epithelial plates, which come from the epithelial processes of the 

 filiform papillae ; the granular cortex, on the other hand, is nothing else than 

 the matrix of a filiform fungus with filaments of only o-ooo6"' in breadth, which 

 take root in it, often in enormous quantities. . 



Respecting the physiology of the papillae of the tongue, the following may 

 be gathered from the anatomical data given above. The filiform papilla: are 

 neither organs of taste, nor fine organs of touch, since their thick, and what 

 I am disposed to lay more stress upon, cornified epithelium is but little 

 adapted to allow of the passage of fluids capable of being tasted, or to con- 

 duct other impressions to the scantily provided nerves, which extend only as 

 far as the base of the simple papilla;. With Todd and Bowman, I consider 

 the filiformes as allied in their functions to the tongue-spines of animals, 

 which are merely modified papillce -filiformes, and am accordingly disposed 

 to regard them as serving more or less for acting mechanically on the food, 

 whilst their epithelium is a protective coating for the tongue. 



The two other kinds of papilla; are subservient to the taste, and are, more- 

 over, the seat of common sensation (for mechanical stimuli, heat and cold, 

 etc.), for which functions they are excellently fitted by their thin, soft epi- 

 thelium, the softness of the tissue of their papilla*, and the superficial 

 position (in the secondary papilla;) and large number of their nerves. Micro- 

 scopical ganglia occur on the branches of the glosso-pharyngeiis and lingualis 

 in the tongue, although it has not yet been ascertained whether they are 

 concerned in the sensations of the tongue, or in the secretion of its glands. 



