16 



SPECIAL HISTOLOGY. 



of connective tissue (see above § 131) ; it has itself a dense and 

 solid appearance, though in consequence of the presence of a 

 considerable quantity of elastic tissue, of common fat cells of 

 0016 — 0'024'", and of its abundant vascular supply, it is tole- 

 rably elastic. 



The papillce filiformes or conicce (fig. 173), are conical pro- 

 cesses of mucous membrane beset either at their extremities 



only, or over their whole 

 surface, with a certain 

 number (5 — 20) of smaller 

 secondary papilla of 0*1 

 — 0-14'" in length. The 

 whole is invested with a 

 thick epithelial coat drawn 

 out at its extremity into 

 a number of long, thin 

 (0-01 — 002 ,// ), fine and 

 often subdivided, processes 

 (fig. 173, /), which give 

 the papilla the aspect of 

 a fine brush, and may 

 attain a length of as much 

 as 05 — 0-6-0-r, with a 

 breadth of 002— 0-028"' 

 at their base. The super- 

 ficial layers of this epi- 

 thelium resemble the epi- 

 dermic plates in their long 

 resistance to the action of 

 acids and alkalies, and 

 consist, especially the epi- 

 thelial processes, only of solid horny scales of 0-022 to 

 0028 /// , which frequently form a more solid axis, and of an 

 external cortex composed of overlapping plates, so that the 

 whole mass may, with some justice, be compared to a hair. 

 The primary papilla of the p. filiformes contains distinct con- 

 Fig. 173. Two papilla filiformes of Man, one with its epithelium, x 35, after 

 Todd and Bowman : p, the papilla themselves; a, v, arterial and venous vessels of 

 papilla, together with the capillary loops, which, however, ought to enter the 

 secondary papilla. 



