450 SPECIAL HISTOLOGY. 



tions towards the secondary papillae, and their axile corpuscles (see 

 37). 



The nerves, which in the trunks measured 0-002-0-004, * on the 

 average 0-003 of a line, diminish in size during their course, so that at 

 the base of the papillae, their diameter is not more than 0-001-0-0015 

 of a line, and they also exhibit distinct divisions ; I have not yet 

 observed their terminations with certainty, but have thought that in 

 some cases I could detect loops, in others, free ends, without, however, 

 pledging myself either to the one or the other. 



In the papillce circumvallatce the central papilla, which may be re- 

 garded as a depressed papilla fungiformis, is closely covered upon its 



plane terminal surface with 

 simple conical elevations, and 

 is invested externally by an 

 epithelium of uniform thick- 

 ness, without any special 

 processes and prolongations. 

 The ivall is a simple elevation 

 of the mucous membrane, 

 possessing a smooth epithelial investment, beneath which its upper bor- 

 der is produced into many rows of simple conical secondary papillae. 

 The elastic tissue is usually absent in the papillae, otherwise, they have 

 the same structure as the fungiform kind, only they are still more abun- 

 dantly provided with nerves. Every proper papilla circumvallata con- 

 tains in its lowest portions several nervous trunks of 0-05-0-08 of a line 

 in diameter, which as they ascend, subdivide into a very elegant plexus, 

 from which the nerves of the secondary papillae radiate upon all sides. 

 In other respects, they resemble the p. fungiformes, except that the 

 nerve-tubules, even in the trunks, have not a greater average diameter 

 than 0-002, and the largest not more than 0-003 of a line, while at the 

 base of the secondary papillae it is not more than 0-001-0-0015 of a line. 

 The walls of these papillae also contain many nerves, whose ultimate 

 disposition appears to be exactly the same as in the papillae themselves. 



The lingual papillae present many varieties, the following of which are 

 the most important: 1. The papillce filiformes are all elongated, and 

 provided with very considerable epithelial processes. The appearance 

 of what is commonly called a gastric furred tongue, depends principally 

 upon the growth of the epithelial processes of the papillce filiformes, 

 which, all directed backwards and in close apposition, form apparently 

 a peculiar white coating. If the processes become longer, so that the 



FIG. 175. Papilla circumvallata of Man in section: ./#, proper papilla; B, wall; a, epithe- 

 lium ; c. secondary papilla : bb, nerves of the papilla and of the wall. Magnified about 10 

 diameters. 



