sponding impairment of the mind.

First of all, it is found that the nervous system has a certain
up-and-down arrangement from the segments of the spinal cord up to the
gray matter of the rind or "cortex" of the large masses or hemispheres
in the skull, to which the word brain is popularly applied. This
up-and-down arrangement shows three so-called "levels" of function.
Beginning with the spinal cord, we find the simplest processes, and
they grow more complex as we go up toward the brain.

The lowest, or "third level," includes all the functions which the
spinal cord, and its upper termination, called the "medulla," are able
to perform alone--that is, without involving necessarily the activity
of the nervous centres and brain areas which lie above them. Such
"third-level" functions are those of the life-sustaining processes
generally: breathing, heart-beat, vasomotor action (securing the
circulation of the blood), etc. These are all called Automatic
processes. They go regularly on from day to day, being constantly
stimulated by the normal changes in the physiological system itself,
and having no need of interference from the mind of the individual.

In addition to the automatic functions, there is a second great class
of processes which are also managed from the third level; that is, by
the discharge of nervous energy from particular parts of the spinal
cord. These are the so-called Reflex functions. They include all those
responses which the nervous system makes to stimulations from the
outside, in which the mind has no alternative or control. They happen
whether or no. For example, when an object comes near the eye the lid
flies to reflexly. If a tap be made upon the knee while one sits with
the legs crossed the foot flies up reflexly. Various reflexes may be
brought out in a sleeper by slight stimulations to this or that region
of his body. Furthermore, each of the senses has its own set of reflex
adjustments to the stimulations which come to it. The eye accommodates
itself in the most delicate way to the intensity of the light, the
distance of the object, the degree of elevation, and the angular
displacement of what one looks at. The taking of food into the mouth
sets up all sorts of reflex movements which do not cease until the
food is safely lodged in the stomach, and so on through a series of
physiological adaptations which are simply marvellous in their variety
and extent. These processes belong to the third l