rough
the much softer tissue of the brain, unenclosed within a _firm bony
case_ as in after-life, varies with far greater rapidity in the infant
than in the grown person, and hence the organ is far more easily
overfilled with or emptied of its blood. Besides, any organ in which
growth is going on with great rapidity is proportionately liable to
become disordered or diseased. Now the brain doubles its weight in the
first two years of life, and attains nearly its full size by the end of
the seventh year.

These two facts suggest a bright as well as a dark view of disorders of
the brain and nervous system in early life. If disorder is more
frequent, it is excited by slighter causes, is more likely to be
temporary, and even its gravest symptoms, such as convulsions and
paralysis, have a less serious import in the one case than in the
others. If the grown man has a fit, and still more, if that fit is
followed by paralysis, we fear and with reason that some vessel in the
brain-substance has given way, or that some grave, probably irreparable
damage has been inflicted on it. In the child, and especially in the
young infant, these accidents may mean nothing more than that the brain
has suddenly become over-filled with blood, or that it has been
disturbed by irritation--I know of no better term--in some distant
organ.

CONVULSIONS.--There are in the body two great nerve masses, the brain
and the spinal cord, through which all parts are brought into relation
with each other. The spinal cord or spinal marrow receives impressions
from all parts, imparts movement to the limbs, as well as gives activity
to the functions of the various internal organs. The brain is the
controlling power, and governs more or less consciously the movements
which the spinal cord originates, and hence in proportion as the
development of the brain advances, and its controlling power increases,
those involuntary movements, fits or convulsions, which originate in
irritation of the spinal cord, become rarer. The brain, at the age of
three years, is more than twice as large as in the first year of life,
and deaths from convulsions have then sunk to a third of their former
frequency; while from the age of ten to fifteen years, when the brain
may be said to be perfected, only four per cent., instead of nearly
eighty per cent. as in the first years of life, of all deaths from
disorders of the nervous system are due to convulsions.[12]

I dwell on this subject