ts of the Vocal Organs to the
Production of Different Sounds.*--1. Lightly grasp the larynx with the
fingers while talking. Observe the changes, both in the position and shape
of the larynx, in the production of sounds of different pitch. 2. Observe
the difference in the action of the muscles of respiration in the
production of loud and faint sounds. 3. Pronounce slowly the vowels, A, E,
I, O, U, and the consonants C, F, K, M, R, S, T, and V, noting the shape
of the mouth, the position of the tongue, and the action of the lips in
each case.

*To demonstrate the Ear.*--Examine a dissectible model of the ear, locating
and naming the different parts. Trace as far as possible the path of the
sound waves and find the termination of the auditory nerve. Note also the
relative size of the parts, and calculate the number of times the model is
larger than the natural ear. _Suggestion_: The greatest diameter of the
internal ear is about three fourths of an inch.

In an extended course it is a profitable exercise to dissect the ear of a
sheep or calf, observing the auditory canal, middle ear, bridge of bones,
and the tympanic membrane with attached malleus and tensor tympanic
muscle. Pass a probe from the nasal pharynx through the Eustachian tube
into the middle ear. With bone forceps or a fine saw, split open the
petrous portion of the temporal bone and observe the cochlea and the
semicircular canals. By a careful dissection other parts of interest may
also be shown.

CHAPTER XXII - THE EYE

Sight is considered the most important of the sensations. It is the chief
means of bringing the body into proper relations with its surroundings
and, even more than the sensation of hearing, is an avenue for the
reception of ideas. The sense organs for the production of sight are the
eyes; the external stimulus is

*Light.*--Light, like sound, consists of certain vibrating movements, or
waves. They differ from sound waves, however, in form, velocity, and in
method of origin and transmission. Light waves are able to pass through a
vacuum, thus showing that they are not dependent upon air for their
transmission. They are supposed to be transmitted by what the physicist
calls ether--a highly elastic and exceedingly thin substance which fills
all space and penetrates all matter. As a rule, light waves originate in
bodies that are highly heated, being started by the vibrations of the
minute particles of matter.

Light is influenced i