Experiment 1. _To examine squamous epithelium._ With an ivory
paper-knife scrape the back of the tongue or the inside of the lips or
cheek; place the substance thus obtained upon a glass slide; cover it
with a thin cover-glass, and if necessary add a drop of water. Examine
with the microscope, and the irregularly formed epithelial cells will be
seen.

Experiment 2. _To examine ciliated epithelium._ Open a frog's
mouth, and with the back of a knife blade gently scrape a little of the
membrane from the roof of the mouth. Transfer to a glass slide, add a
drop of salt solution, and place over it a cover-glass with a hair
underneath to prevent pressure upon the cells. Examine with a microscope
under a high power. The cilia move very rapidly when quite fresh, and
are therefore not easily seen.

For additional experiments which pertain to the microscopic examination of
the elementary tissues and to other points in practical histology, see
Chapter XV.

[NOTE. Inasmuch as most of the experimental work of this chapter
depends upon the use of the microscope and also necessarily assumes a
knowledge of facts which are discussed later, it would be well to
postpone experiments in histology until they can be more
satisfactorily handled in connection with kindred topics as they are
met with in the succeeding chapters.]