1 64 TUCKERMAN. j>'oL. IV. 



terior part. The two divisions are of nearly equal length, the 

 total length of the organ being 55 mm. The anterior division 

 is 15 mm. in breadth, 10 mm. in thickness, and is free from the 

 floor of the mouth for 14 mm. The upper surface and sides 

 of this division are covered with small, densely packed, cone- 

 shaped papillae, the apices of which are directed backwards. 

 The epithelium sheathing the papillae is dense and imbricated, 

 and in their upper half either partly or wholly cornified. The 

 papillate surface is impressed by a mesial furrow, extending 

 from the anterior limits of the posterior division nearly to the 

 tip. The tip is short, broad, and obtuse. The under surface is 

 somewhat wrinkled, and marked by a longitudinal median ridge. 

 Fungiform papillae are not especially numerous. They are 

 rather sparingly distributed over the anterior dorsal surface, and 

 the posterior division of the organ appears to be nearly destitute 

 of them. About the tip, however, particularly over its inferior 

 part, they are of good size and fairly abundant. The posterior 

 division, which rises somewhat abruptly above the level of the 

 preceding, is 13 mm. in breadth, and about the same in thick- 

 ness. The upper surface is somewhat convex, and, in front of 

 the circumvallate area, is covered with closely set mechanical 

 papillae, the points of which are directed backwards. The two 

 circumvallate papillae are placed one on either side of the median 

 line, and are 6 mm. apart. The lateral gustatory organs (papillae 

 foliatae) are situated obliquely on each side of the back of the 

 tongue, anterior to the glosso-palatine arch and circumvallate 

 papillae, their anterior extremity being directed downwards and 

 inwards. They are 5 mm. long, and, at their anterior end, 

 3 mm. in breadth. Viewed from above, they are small, convex 

 elevations, their lateral contours converging and forming an 

 apex at the posterior limits of the organ. 



Gustatory Structures. 



The Circumvallate Papillce. — The general surface in front of 

 the papillae is covered with small papillary elevations. The 

 immediate area around them, however, is unpapillate. They 

 measure 0.60 mm. in diameter, and are a trifle less in height. 

 They are flattened on top, and the trenches which encircle them 

 are narrow and of uniform width. Mucous glands are very 

 plentiful, more so than those of the serous type. The ducts of 



