thoroughly understood. This reaction is so constant, so intricate, and
so complex that it is at times difficult to say which is cause and
which effect. Does the depressed state of the mind cause the
indigestion, or is a torpid liver the real seat of the melancholia?

The brain is the most delicately constructed organ in the entire body.
In the lower animals the brain is simply the great nerve-center which,
with its prolongation the spinal cord, presides over all the functions
of life which differentiate the animal from the vegetable. In the
human being the brain is much more highly developed and complicated;
and is, in addition, the seat of the mind, the intellect, and the
affections. Like all the other tissues of the body, the brain receives
its nourishment from the blood-vessels which pass through it, and its
healthy maintenance is in a direct ratio to the condition of its
blood-supply.

A most interesting psychologic study is found in the case of cerebral
paralysis of young children, where there is mental defect amounting to
stupidity or imbecility, accompanied by extensive paralysis of the
body, so that the child is not able to sit up. With the gradual
improvement of the physical condition, so that the muscles become firm
and the child can sit, stand, and even walk, there is a corresponding
mental development; from being stupid and dull, the expression of the
face brightens and becomes intelligent; the child talks quite as well
as other children of its age, and sometimes becomes really
intellectually precocious. Here we see the development of the brain as
a direct result of the improved physical condition. In certain cases
of insanity, on the contrary, we find that the wasting away of the
body results from the disease of the brain, i. e., the disease of the
brain has wrought the wreck of the body.