al branches of the thoracic ganglia.
G, H, The right and left coronary plexus, situated upon the heart. I, N,
Q, The inferior, middle, and superior cervical ganglia. 1, The renal
plexus of nerves that surrounds the kidneys. 2, The lumbar ganglion. 3,
Their internal branches. 4, Their external branches. 5, The aortic plexus
of nerves that lies upon the aorta. The other letters and figures
represent nerves that connect important organs and nerves with the
sympathetic ganglia.]

766. The GANGLIA may be considered as distinct centres, giving off
branches in four directions; namely, the superior, or ascending, to
communicate with the ganglion above; the inferior, or descending, to
communicate with the ganglion below; the external, to communicate with
the spinal nerves; and the internal, to communicate with the
sympathetic filaments. It is generally admitted that the nerves that
pass from the ganglia are larger than those that entered them; as if
they imparted to the nerve some additional power.

767. The branches of distribution accompany the arteries which supply
the different organs, and form communications around them, which are
called plexuses, and take the name of the artery with which they are
associated. Thus we have the mesenteric plexus, hepatic plexus,
splenic plexus, &c. All the internal organs of the head, neck, and
trunk, are supplied with branches from the sympathetic, and some of
them exclusively; for this reason, it is considered a nerve of organic
life.

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What is the design of fig, 131? 766. How may the ganglia be
considered? 767. What is said of the branches of the sympathetic
nerve?

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CHAPTER XXXVIII.

PHYSIOLOGY OF THE NERVOUS SYSTEM.

768. The brain is regarded by physiologists and philosophers as the
organ of the mind. Most writers consider it as an aggregate of parts,
each charged with specific functions, and that these functions are the
highest and most important in the animal economy. To the large brain,
or cerebral lobes, they ascribe the seat of the faculties of
_thinking_, _memory_, and _the will_. In man, this lobe extends so far
backward as to cover the whole of the cerebellum. To the cerebellum,
or little brain, is ascribed the seat of the _animal_, or _lower
propensities_.

769. "The constant relation between mental power and development of
brain, explains why capacities and dispositions are so different. In
infancy, f