256 TASTE BUDS. [BOOK in. 



the sides of the circumvallate papillae, and still less regularly 

 on the fungiform papillae. 



Each taste-bud consists on the outside of an oval hollow 

 structure, which may be compared to an oval nest, the walls of 

 which are formed of epithelial cells arranged thatch-wise. The 

 base of the nest lies bare on the dermis, the top of the nest 

 comes to the level of the surface of the epithelium, and here 

 bears a circumscribed circular hole, or mouth by means of which 

 the fluids of the mouth can gain access to the inside of the nest. 

 The cells forming the walls are elongated, flattened, fusiform, 

 appropriately curved, nucleated cells, arranged in an imbricate 

 fashion, the outer ones passing somewhat abruptly into the 

 ordinary cells of the malpighian and corneous layers. Those 

 ends of the cells which converge to form the top of the nest are 

 scooped out, or bear distinct perforations, and thus in the one 

 way or the other, form the margin of the mouth or pore leading 

 to the inside of the nest. The cell-substance forming the 

 scooped margin or surrounding the perforation seems to be cuti- 

 cularized so as to secure the patency of the pore. 



The cells thus forming the walls of the nest differ from the 

 surrounding ordinary cells chiefly in form ; at least they cannot 

 be spoken of as distinctly modified in respect to their actual 

 nature. The interior of the nest however is occupied by cells, 

 which we must regard as specialized sensory cells. These are of 

 two kinds. The one kind, very similar to the rod cells of the 

 olfactory organ, are called rod cells; the other kind, analogous 

 to the cylinder cells of the olfactory organ, we may call subsidiary 

 cells ; they have also been called " cover-cells." The rod cell 

 consists of an elongated oval nucleus placed vertical, at about the 

 level of the middle of the nest. The scanty cell-substance sur- 

 rounding the nucleus is prolonged peripherally as a rod shaped 

 nearly hyaline, somewhat refractive process which reaches up, or 

 projects through the pore of the nest ; the cell-substance is also 

 prolonged centrally as a delicate thread-like process, which either 

 branching or unbranched, stretches towards and is lost to view at 

 the dermis. 



The subsidiary cell possesses a nucleus which is larger and 

 more rounded than that of the rod cell, and its cell-substance 

 larger in amount and more granular in appearance than that of 

 the rod cell, has a more or less fusiform shape, the part peripheral 

 to the nucleus ending in a tapering fashion, and the part on the 

 other, central, side of the nucleus becoming branched and lost to 

 view near the dermis. 



The axis of the nest is occupied by a group of rod cells, the 

 peripheral processes of which converge in a bunch at the pore of 

 the nest. With these however are interspersed a few subsidiary 

 cells, and the core thus formed is surrounded by a wrapping con- 

 sisting of subsidiary cells only. Both the rod cells and subsidiary 



