section removed. Split
it open for a part of its length, and wash out its contents. Observe its
coats. Place it in a shallow vessel containing water, and examine the
mucous membrane with a lens to find the _villi_. Make a drawing of this
section, showing the coats.

9. Study the connection of the small intestine with the large. Split them
open at the place of union, wash out the contents, and examine the
ileo-caecal valve.

10. Observe the size, shape, and position of the kidneys. Do they lie in
front of or back of the peritoneum? Do they lie exactly opposite each
other? Note the connection of each kidney with the aorta and the inferior
vena cava by the renal artery and the renal vein. Find a slender tube, the
_ureter_, running from each kidney to the bladder. Do the ureters connect
with the top or with the base of the bladder? Show by a sketch the
connection of the kidneys with the large blood vessels and the bladder.

*To demonstrate the Teeth.*--Procure from the dentist a collection of
different kinds of teeth, both sound and decayed.

(_a_) Examine external surfaces of different kinds of teeth, noting
general shape, cutting or grinding surfaces, etc. Make a drawing of an
incisor and also of a molar.

(_b_) After soaking some of the teeth for a couple of days in warm water
saw one of them in two lengthwise, and another in two crosswise, and
smooth the cut surfaces with fine emery or sand paper. Examine both kinds
of sections, noting arrangement and extent of dentine, enamel, and pulp.
Make drawings.

(_c_) Examine a decayed tooth. Which substance of the tooth appears to
decay most readily? Why is it necessary to cut away a part of the tooth
before filling?

(_d_) Test the effect of acids upon the teeth by leaving a tooth over
night in a mixture of one part hydrochloric acid to four parts water, and
by leaving a second tooth for a couple of days in strong vinegar. Examine
the teeth exposed to the action of acids, noting results.

*To show the Importance of Mastication.*--Fill two tumblers each half full
of water. Into one put a lump of rock salt. Into the other place an equal
amount of salt that has been finely pulverized. Which dissolves first and
why?

*To illustrate Acid and Alkaline Reactions.*--To a tumbler half full of
water add a teaspoonful of hydrochloric or other acid, as vinegar. To a
second tumbler half full of water add an equal amount of cooking soda.
Taste each liquid, noting the sour taste o