496 THE SOLIDS. 



This chain of papillae forms the extreme boundary of the 

 space over which the sense of taste extends, the surface be- 

 hind it being smooth, non-papillary, and exhibiting numerous 

 openings of mucous glands ; thus then it would appear we 

 have a true gustatory region. 



Each compound papilla is made up of numerous simple 

 papillae, arranged differently in the case of the three forms 

 of these already enumerated. 



The filiform papillae are by far the most numerous, being 

 more than in the proportion of twenty to one ; when freed 

 from epithelium they are seen to be more or less cylindrical 

 in form, and to consist of a variable number of simple pa- 

 pillae from sixteen to twenty or more to each, arranged in a 

 single circular series, forming the top and margin of the 

 cylinder. (See Plate LXIV./#. 3.) The sides of the simple 

 papillae are more or less united together, but the tips are free 

 and pointed, some more so than others. 



The length of the cylinder which each filiform papilla 

 describes, the degree of acumination of the apices of the 

 secondary papillae, and the extent of these which is free, 

 varies in accordance with the position of the papillae on the 

 tongue. 



The circular disposition referred to is best seen in the pa- 

 pillae placed near the tip and sides of the tongue, for in those 

 situations the secondary papillae are short, blunt, and nearly 

 of equal lengths. (See Plate LXIV. Jig. 3.) In the centre 

 of the organ the simple or secondary papillae are much longer, 

 and more slender, so that they fall together and variously inter- 

 mix with each other, and thus it is that the circular disposi- 

 tion in them is usually more or less concealed from view. 

 (See Plate LXIV. fig. 4.) 



This disposition of the secondary papillae includes of course, 

 as a consequence, a corresponding arrangement of the blood- 

 vessels, (a single looped vessel proceeding to each), and of the 

 nerve filaments, which are in like manner arranged in circles. 

 (See Plate LXVI. fig. 4.) 



The centre of each filiform papilla is hollowed out, and is 

 to be regarded as a large mucous follicle, and thus the com- 



