V. The Atomic Theory says that no two molecules of matter, as the paper, are in close contact. In the spaces between the molecules, called pores, is supposed to be an imponderable substance, ether, which, though it has none of the properties of matter, we think as existing. Ether seems to occupy all the spaces that are not filled by matter, those between us and the heavenly bodies as well as intermolecular spaces.

PRESENTATION STEP.-I. I just heard a bell ring, that is, I had a group of sound sensations. Think what had to take place before I could hear these sounds:

The first thing was the striking together of two pieces of metal, the clapper and the bell, in such a way that vibrations of a rapid rate were started in both the bell and the clapper. Next, these vibrations, or waves were transmitted in straight lines by means of the air and other matter in all directions from the bell. Imagine these spheres of motion moving out from the bell as a centre through the air, the walls, the earth, and everything in their way. In the course of time some of this motion reaches my ear-drums, is transmitted through the parts of my ears to my auditory nerves, and thus to certain cells in the temporal lobes of my brain. So far there have been only vibrations of matter. Now, apparently, a wholly new result takes place, in that I have a sensation of sound in my mind.

No one has yet explained how vibrations of matter are turned into a mental state, a sensation. We have to accept the experience as a fact without any explanation. The result then of this particular kind of brain excitation is a sensation of sound in my mind.

II. Let us study next a sensation of smoothness, the touch of my pen:

As my finger tip moves over the pen, changes take place in the terminals of the nerves of touch in my skin. This excitation is transmitted along the length of the nerves of touch through my arm, body, and spinal cord to certain brain cells, and the result in my mind is sensations of smoothness.

III. What takes place in order that we may have a sensation of color is rather more complex. It is perhaps somewhat as follows:

I see the color green of my blotter. The vibrations we are concerned with here originate in the solid particles of carbon in a lamp flame. As compared with those that vibrate when the result is sound, these particles are vibrating at an intense rapidity. The waves thus started are transmitted in straight lines in all directions from the vibrating particles in the flame by the medium ether. Some of the vibrations are reflected from the blotter, though at a changed rate, through my eye,-its lenses and humors to the retina. Excitation is set up in the optic nerve and brain cells, and the result in my mind is the sensation

green.

It is probable, also, that when the source of vibration is the sun or any other body in intense enough vibration, the process and medium are the same.

IV. We have studied what takes place when we have sensations of sound, touch, and color only. What occurs in case of the other kinds of sensation is probably analogous. When the sensations are secondary, (recalled, inner) though the end organs and nerves seem not to be excited, the brain-cells are active.

In each case noticed the analysis of what precedes a sensation ends with the words, "the result in mind (of the cerebral excitation) is a sensation of sound, color, or touch."

A generalized form of this statement may be accepted as the definition of a sensation :

The result in mind of cerebral excitation is a sensation.

APPLICATION STEP.-I. Imagine your condition without color sensations. In what terms must a blind man do his thinking? How would you think the thoughts of the last hour without sound sensations? Suppose that you had no sensations at all!

II. Observation of the sensations that you use in thinking will soon show you that there are many more kinds than just those of the five senses of the older psychology. The "five gates of Mansoul" are no longer adequate to furnish our complex mental life. Besides the sensations of these senses, we have those from the organs of the body, that is, organic sensations (such as tooth-ache, closeness, fatigue, hunger), sensations of temperature, pressure, and those from the tendons and joints.

III. The body is like a quivering, sensitized soundingboard, each sense of which responds to its own rate of stimulus. Though not all stimuli result in active consciousness as discriminated sensations, or mental states, each modifies the others and is in turn modified by them, so that the stream of thought at any moment is the resultant of all the bodily stimuli.

IV. The fact that different sensations are the mental results of different rates of vibration in matter seems to indicate that the different senses had a common origin. And indeed such is apparently the case.

The spinal cord and the entire nervous system are believed to have developed from the external embryological layer, the skin, and all the higher senses have arisen as gradually differentiated and specialized forms of touch, the "mother tongue" of the senses.

V. Why do we not hear sounds from the sun, Jupiter, or the morning stars?"

"

VI. Suppose your auditory nerve had always vibrated at the same rate: Would there have been a sensation resulting from this particular excitation?

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We must think that there would not. Change seems to be necessary to attract our attention. In fact, all sensation might be defined as "consciousness of change." chain of consciousness is a sequence of differents Hodgson, The Philosophy of Reflection ").

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VII. Here again, as in the study of associations, the caution is necessary that, though for convenience in analysis. we have spoken of sensations as if they were separate realities, perhaps somewhat like the atoms of matter, they must not be thought of as such.

"No one of them " (mental elements) can live out of that particular thought, any more than my head can live off of my particular shoulders. In a sense a soap-bubble has parts; it is a sum of juxtaposed spherical triangles. But these triangles are not separate realities; neither are the 'parts' of the thought separate realities. Touch the bubble and the triangles are no more. Dismiss the thought and out go its parts. You can no more make a new thought out of ideas' that have once served than you can make a new bubble out of old triangles. Each bubble, each thought, is a fresh organic unity, sui generis." ("Psychology," Vol. I, W. James.)

VIII. Study your stream of thought as though it were made entirely of sensational elements, that is, as though all thinking and experience were in the terms of colors, sounds, touches, tastes, smells, temperatures, and organic sensations. “All thought is the action and interaction of sensations."

Someone has likened sensations to the letters of the alphabet, which have spelled out all of literature; so our sensations spell out for us all our experience, both inner and outer, or primary and secondary.

Learn by daily study this alphabet of mental life; -name and make lists of the elements of many trains of association. Make lists also under each sense of as many sensations as you notice, and analyze what precedes each.

LESSON II

THE SENSE OF SOUND

PREPARATION STEP.-I. Name the sounds you have noticed during the last hour.

II. The analysis of what precedes the sound sensations of a piano I hear is as follows: Hammers controlled by means of a mechanism through the keys of the piano are caused to strike the wires stretched over a sounding-board in the piano case. The wires vibrate as a result, and the air transmits the motion from them in all directions. Some of the waves strike the sounding-board which so collects and reflects them that they are intensified. As reflected these waves travel in all directions through matter, that is, the air, the floor, and the walls of the room and the house, and some of them finally reach my ear. Excitation is set up in the auditory nerve and brain-cells, and there is a result in mind of sensations of sounds.

Go over again and again some similar analysis for yourself, imagining vividly what takes place and tracing with your finger the lines of vibration that come to your ears.

III. Analyze what precedes many different sounds, as voices, the wind, the rain.