This section is from the book "Applications of Psychology to the Problems of Personal and Business Efficiency", by Warren Hilton. Also available from Amazon: Psychology and Achievement - Applied Psychology 12 Volume Set.
WE HAVE been considering the relationship between mind and body from the standpoint of the mind. Our investigation has been largely introspective; that is to say, we simply looked within ourselves and considered the effects of our mental operations upon our own bodies. The facts we had before us were facts of which we had direct knowledge. We did not have to go out and seek them in the mental and bodily activities of other persons. We found them here within ourselves, inherent in our consciousness. To observe them we had merely to turn the spotlight into the hidden channels of our own minds.
We come now to examine the mind's influence upon the body from the standpoint of the body. To do this we must go forth and investigate. We must use eye, ear and hand. We must use the forceps and scalpel and microscope of the anatomist and physiologist.
But it is well worth while that we should do this. For our investigation will show a bodily structure peculiarly adapted to control by a governing consciousness. It will reveal to the eye a physical mechanism peculiarly fitted for the dissemination of intelligence throughout the body. And, most of all, it will disclose the existence within the body of subordinate mental units, each capable of receiving, understanding and acting upon the intelligence thus submitted. And we shall have strongly corroborative evidence of the mind's complete control over every function of the body.
Examine a green plant and you will observe that it is composed of numerous parts, each of which has some special function to perform. The roots absorb food and drink from the soil. The leaves breathe in carbonic acid from the air and transform it into the living substance of the plant. Every plant has, therefore, an anatomical structure, its parts and tissues visible to the naked eye.
Put one of these tissues under a microscope and you will find that it consists of a honeycomb of small compartments or units. These compartments are called "cells," and the structure of all plant tissues is described as "cellular." Wherever you may look in any plant, you will find these cells making up its tissues. The activity of any part or tissue of the plant, and consequently all of the activities of the plant as a whole, are but the combined and co-operating activities of the various individual cells of which the tissues are composed. The living cell, therefore, is at the basis of all plant life.
In the same way, if you turn to the structure of any animal, you will find that it is composed of parts or organs made up of different kinds of tissues, and these tissues examined under a microscope will disclose a cellular structure similar to that exhibited by the plant.
Look where you will among living things, plant or animal, you will find that all are mere assemblages of cellular tissues.
Extend your investigation further, and examine into forms of life so minute that they can be seen only with the most powerful microscope and you will come upon a whole universe of tiny creatures consisting of a single cell.
Indeed, it is a demonstrable fact that these tiny units of life consisting of but a single cell are far more numerous than the forms of life visible to the naked eye. You will have some idea of their size and number when we tell you that millions may live and die and reproduce their kind in a single thimbleful of earth.
Every plant, then, or every animal, whatever its species, however simple or complicated its structure, is in the last analysis either a single cell or a confederated group of cells.
All life, whether it be the life of a single cell or of an unorganized group of cells or of a republic of cells, has as its basis the life of the cell.
For all the animate world, two great principles stand established. First, that every living organism, plant or animal.
big or little, develops from a cell, and is itself a composite of cells, and that the cell is the unit of all life. Secondly, that the big and complex organisms have through long ages developed out of simpler forms, the organic life of today being the result of an age-long process of evolution.
What, then, is the cell, and what part has it played in this process of evolution?
To begin with, a cell is visible only through a microscope. A human blood cell is about one-three-thousandth of an inch across, while a bacterial cell may be no more than one-twenty-fivc-thou-sandth of an inch in diameter.
Yet, small as it is, the cell exhibits all of the customary phenomena of independent life; that is to say, it nourishes itself, it grows, it reproduces its kind, it moves about, and it feels. It is a living, breathing, feeling, moving, feeding thing.
The term "cell" suggests a walled-in enclosure. This is because it was originally supposed that a confining wall or membrane was an invariable and essential characteristic of cell structure. It is now known, however, that while such a membrane may exist, as it does in most plant cells, it may be lacking, as is the case in most animal cells.
The only absolutely essential parts of the cell are the inner nucleus or kernel and the tiny mass of living jelly surrounding it, called the protoplasm.
The most powerful microscopes disclose in this protoplasm a certain definite structure, a very fine, thread-like network spreading from the nucleus throughout the semi-fluid albuminous protoplasm. It is certainly in line with the broad analogies of life, to suppose that in each cell the nucleus with its network is the brain and nervous system of that individual cell.
All living organisms consist, then, simply of cells. Those consisting of but one cell are termed unicellular; those comprising more than one cell are called pericellular.