HISTOLOGY OF NERVE TISSUES 63 
parts. Select also a good longitudinal section through the middle 
of a corpuscle. Draw each view. 
Taste Buds, in the Epithelium of the Tongue (sections through 
the foliate papillae of the rabbit are recommended).—Note that the 
surface of the tongue is covered by a thick epithelium consisting 
of many layers of cells closely packed together. Note the differ¬ 
ence in shape of the cells of the superficial and deeper layers. In 
the epithelium which covers certain conspicuous folded regions 
(foliate papillae) identify the taste buds, each of which is a cluster 
of much elongated cells with their long axes at right angles to the 
surface of the fold. These differentiated epithelial cells are of two 
sorts, gustatory or taste cells and supporting cells. The gustatory 
cells, within the taste bud, are surrounded by the end arborizations 
of nerve fibers, which are rendered visible only by special methods 
of staining. Other branches of nerve fibers end among the cells 
between the adjoining taste buds. At its outer end each gustatory 
cell possesses a cilium which projects slightly from the surface 
through the opening of the organ, known as a taste pore. Draw 
a single good section through a taste bud , showing the relation of the 
cells to this pore. 
Olfactory Epithelium (teased or dissociated preparations are 
recommended; also sections of olfactory epithelium of some 
amphibian, stained with iron haematoxylin or other stain espe¬ 
cially adapted to bring out nerve cells and fibers).—The olfactory 
organ is peculiar in that there are present among certain tall 
columnar epithelial cells, other tall cells which are nervous in 
nature. Each of these has a short process (dendrite) which extends 
to the free surface, and another much elongated process (neurite) 
which is an olfactory nerve fiber and extends to the olfactory lobe 
of the brain. In the preparations supplied distinguish the two 
sorts of cells and draw a few of each , either in place or dissociated. 
The Retina 1 (slides showing vertical sections through the 
retina, e.g., of the rabbit and the frog).—Under the low power note 
that the staining methods used have disclosed the fact that the 
retina consists of many layers of structures of different thickness in 
different regions. Examine a carefully selected region under high 
1 This study of the retina may conveniently be postponed until after the study of 
the eyeball (p. 88). 
