s also
accompanied by greater elaboration of the ganglionic nerves supplying
the viscera, upon whose efficient action the nutrition of this frame
depends. But beyond a certain point in the ascending scale, the
exactness of this correlation ceases. The muscles and bones are smaller;
yet the structure of the cerebro-spinal organs, especially the brain,
becomes more elaborate; and hence the control exercised over the
functions of the ganglionic system is more complete, although the
relative size of the two systems is not much changed.

Such control or predominance is manifested in the following ways: First.
The functions of animal life, presided over by the cerebro-spinal
system, become proportionately more important than those of vegetative
or nutritive life, carried on by the ganglionic. That is to say, the
acts of locomotion sustained by the spinal cord and the nervo-muscular
apparatus, and the intellectual acts of the thought and will, sustained
by the brain--are relatively more prominent than are the acts of
digestion, respiration, circulation, etc., dependent on the functions of
the ganglionic nerves. Second. These latter functions are themselves
effected with more regularity and more force, when the activity of the
cerebro-spinal system predominates over that of the ganglionic. Within
certain limits, this is so true, that human beings possess over lower
animals a superiority, not only of intellect, but of capacity for
digesting various articles of food; and of maintaining their temperature
in more various states of the external atmosphere. Third. Finally, the
actions of the cerebro-spinal system, intellectual and muscular, are
more regular and powerful when not liable to interruption from the
operations of the ganglionic nerves, and the visceral functions presided
over by them. When the boa-constrictor digests, he falls into a state of
torpor that exceeds in degree, but not in kind, the drowsy rumination of
a cow chewing her cud. Such animals are slaves to their nutritive
functions, by which those of the brain and spinal cord may at any time
be, as it were, oppressed and overwhelmed. The capacity for independence
increases with every rise in the hierarchical scale of vertebrates,
until it culminates in man--able to think and talk over his dinner; to
manufacture heat in his limbs while drawing blood to his cerebral
hemispheres; to sustain in complete unconsciousness innumerable delicate
and complicated chemical metam