456 EDWARD B. POULTON. 



the papillate surface on the tip of the tongue^ project horizontally 

 or slightly downwards. They have swollen rounded ends and 

 constricted bases, and the superficial layer of cells is not corni- 

 fied. They are especially large in front, and resemble the 

 ordinary type of fungiform papilla. These papilla3 contain 

 especially large meduUated nerves, which are accompanied by 

 blood-vessels. Behind these papillae, in front and at the sides, 

 occur others of a conical shape, with constricted bases and fine 

 recurved cornified apices. Their anterior surface is convex, and 

 thecornified layer of the apex extends downwards upon it for a 

 short distance, while the posterior surface is less convex, and 

 the cornified cells descend almost to the superficial epithelium 

 of the tongue. There are many rows of these papillae, and they 

 become gradually lower, broader, and more scale-like posteriorly, 

 with a sharp crescentic ridge of cornified cells on their apices, di- 

 rected transversely to the long axis of the tongue. The arrange- 

 ment is very regularly imbricate. The layer of cornified cells 

 is now much thicker, and forms the important part of the an- 

 terior and posterior surfaces, while the shape gradually assumes 

 that shown in longitudinal section in fig. 6, and is singularly 

 like that of the teeth of a rasp. This form passes on into the 

 posterior subregion. The anterior papillae are about 1 mm. in 

 height, while posteriorly they decrease till at the limits of the 

 subregion they are not more than '3 mm. in height. The epi- 

 thelium is very simple in structure, a stratum corneum being 

 entirely absent, and the superficial cells being fusiform with 

 distinct nuclei. The layer appears to represent the rete Mal- 

 pighii only. Occasionally little isolated groups of cornified cells 

 occur at some depth beneath the surface, and surrounded on 

 all sides by non-cornified cells. Papillary processes are absent 

 in front, where the papillae are thickly placed, occasionally 

 present behind, as very long and narrow upgrowths between 

 the less numerous papillae. 



The epithelium of the papillae is always penetrated by secon- 

 dary papillary processes, which are sometimes very long and 

 narrow. There are traces of the existence of a few hair-like 

 papillae between those of ordinary type at the posterior limits 



