to develop the ellipsis and
explain the facts upon which, if anywhere, this theory is based.

The nervous system, though in many respects a unit, consists of two
great sections, called respectively, the ganglionic system, and the
cerebro-spinal; the latter formed by the brain, the spinal cord, and the
medulla-oblongata, that connects them; the former, constituted by
smaller masses of nervous matter distributed in three ways: First, in a
double chain lying on each side of the spinal cord, from the upper part
of the neck to the pelvic cavity that terminates the trunk. These masses
are called especially the sympathetic ganglia. Second, in so-called
plexuses, occupying different positions in the cavity of the trunk, and
standing in especial relation to various organs; the solar or coeliac
plexus to the stomach, liver, and spleen; the two renal plexuses to the
kidneys; the mesenteric plexuses to the intestine; finally, on each side
of the pelvis, the hypogastric plexus to the bladder, uterus, and
ovaries--the so-called genito-urinary organs. Third, besides these
principal ganglia exist others, much more minute, imbedded in the
muscular walls of certain organs--as the heart (intro-cardiac ganglia),
the intestine (intestinal ganglia).

Each of these nervous masses contains nerve-cells as well as
nerve-fibres, and is capable of generating nerve-force. Each, therefore,
acts like a minute brain; and, in fact, the entire ganglionic system of
nerves is analogous to the nervous system of certain among the lower
animals--the crustacea and mollusks. These possess neither brain nor
spinal cord; their nerve-centres, instead of being concentrated in a
cranium and vertebral canal, are entirely disseminated through the
cavities of the trunk, as are the visceral plexuses in vertebrated
animals. In these, however, the addition of a brain and spinal cord to
the original rudimentary nervous system, powerfully modifies and
controls the action of the latter. The degree of control is variable,
according to the relative predominance of the one or the other; and this
predominance varies, not only according to different species of
vertebrated animals, but also according to different individuals, in
that which presents the most conspicuous capacity for individual
variation--the human species. Up to a certain point, increased
development of the cerebro-spinal system, attended by an increased
development of the osseo-muscular framework of the body, i