ig. 65, _b_.) If we divide the
forehead by vertical lines, as shown in Fig. 71, the divisions thus
formed represent respectively, the Active, Deliberative, and
Contemplative departments of the intellect, all the processes of which
are sustained by vital changes, the transformation of organized
materials. No mental effort can be made without waste of nervous matter.
The gardener's hoe wears by use, and so does every part of the animal
organism. Otherwise, nutrition would be unnecessary for the adult. The
production of thought wears away the cerebral substance. In ordinary
use, the brain requires one-fifth of the blood to support its growth and
repair. Great mental efforts are attended by a corresponding expenditure
of vital treasures, which are abstracted from the total forces available
for the necessities of the system. To repair the losses thus occasioned,
materials are appropriated from the blood, which furnishes supplies in
proportion to the demands made by the mental activities. The production
of thought wears away the gray matter of the cerebrum as surely as the
digging of a canal wears away the iron particles of the spade. The brain
would soon wear out did not the nutritive functions constantly make good
the waste. The intellect, whether engaged in observation,
generalization, or profound study consumes the brain and blood, hence
intellectual activity implies VITAL EXPENDITURE. _Expenditure_ is an
emphatic word because all functions are essential to the production of
this nerve-energy, which returns to the system no equivalent. Physical
exercise, although attended by structural waste, is advantageous to the
circulation of the blood, nutrition, secretion, and, in fact, beneficial
to all the organic processes. This is not true of vigorous and prolonged
mental labor, which is not attended by any of these incidental
advantages. If a child attends a school in which mental development
supersedes physical culture, an inordinate ambition sways the youthful
mind, and its baneful effects upon the health soon become manifest.
Rigorous application of the intellectual faculties consumes the blood,
exhausts the vital forces, weakens the organic functions, while pallor
covers the face, and the eyes sparkle with a hectic radiance. The family
physician pronounces the condition _Anaemia_ (a deficiency of red
corpuscles in the blood), and this change in the quality of the blood is
owing to the undue appropriation by the brain. Convers