FIG. 16.—Diagram illustrating the paths of association.If, however, instead of avoiding the puddle unconsciously, I do so from
consideration of the danger of wet feet and the disagreeableness of soiled shoes
and the ridiculous appearance I shall make, then the current cannot take the short
circuit, but must pass on up to the cortex. Here it awakens consciousness to take
notice of the obstruction, and calls forth the images which aid in directing the
necessary movements. This simple illustration may be greatly complicated,
substituting for it one of the more complex problems which are continually
presenting themselves to us for solution, or the associated trains of thought that
are constantly occupying our minds. But the truth of the illustration still holds.
Whether in the simple or the complex act, there is always a forward passing of
the nerve current through the sensory and thought centers, and on out through
the motor centers to the organs which are to be concerned in the motor response.
The Factors Involved in a Simple Action.—Thus it will be seen that in the
simplest act which can be considered there are the following factors: (1) The
stimulus which acts on the end-organ; (2) the ingoing current over an afferent
nerve; (3) the sensory or interpreting cells; (4) the fibers connecting the sensory
with a motor center; (5) the motor cells; (6) the efferent nerve to carry the
direction for the movement outward to the muscle; (7) the motor response; and,