14 THE GUSTATOEY ORGANS, BY TH. W. EXGELMAXX. 



of the mucous membrane, and connected with dark-bordered nerves 

 that become pale fibres at the point of junction with the vesicles. The 

 axis-cylinder traverses "the nipple-shaped process, filled with proto- 

 plasm, and branches dichotomously on the internal surface of the 

 vesicle. ''Prismatic highly refractile corpuscles (terminal nerve cor- 

 puscles), closely resembling the rods of the retina, are attached to 

 these branches. The vesicles themselves are filled by a watery, bright ? 

 granular mass." The processes of the second kind are tubular ever- 

 sions of the membrane of the vesicles, extending towards the surface 

 between the horny epithelial cells. Their ends always remain covered 

 by a layer of epithelial cells, though this may be extremely thin. 

 Letzerich was not able to find the gustatory organs discovered by 

 Loven and Schwalbe. 



6. GUSTATORY ORGANS OF THE AMPHIBIA. 



The gustatory organs of Birds and Reptilia are still almost 

 unknown in comparison with the far better known and long 

 since described organs of Batrachia (Rana esculenta and tem- 

 poraria, Hyla arborea). In Frogs also the terminal organs of 

 the gustatory nerves are microscopically small clusters of pecu- 

 liarly formed epithelial structures occupying spaces between 

 the epithelial cells of the lingual and palatal mucous membrane. 

 Their form, however, is not that of a flask or bulb, as in Mam- 

 mals, but disk-like. As they completely correspond to the 

 gustatory bulb, we shall term them gustatory disks. They are 

 distributed by hundreds, and with tolerable uniformity, over the 

 upper surfaces and borders of the tongue. Each is here sup- 

 ported by a broad somewhat cylindrical papilla. Numerous gus- 

 tatory disks occur also in the epithelium covering the smooth 

 non-papillated surface of the palatal mucous membrane. These 

 do not project, or project but slightly, beyond the level of the 

 remaining epithelium, and require further investigation. 



MINUTE ANATOMY OF THE GUSTATORY PAPILLAE OF THE FROG 

 (Rana esculenta and temporaria). These papillae consist of a 

 connective-tissue body invested by epithelium, which in gene- 

 ral has the form of a short cylinder or truncated cone. The 

 gustatory disk is seated upon the circular or elliptical terminal 

 surface of this body, surrounded by a narrow girdle of ciliated 



