arts is affected, the
same nerves, the same muscles, and the symptoms or character have a
strict resemblance."

790. The seventh pair of nerves not only communicates the purposes of
the will to the muscles of the face, but at the same time it calls
them into action, under the influence of instinct and sympathy. On
this subject a late writer remarks, "How expressive is the face of
man! How clearly it announces the thoughts and sentiments of the mind!
How well depicted are the passions on his countenance! tumultuous
rage, abject fear, devoted love, envy, hatred, grief, and every other
emotion, in all their shades and diversities, are imprinted there, in
characters so clear that he that runs may read! How difficult, nay,
how impossible, is it to hide or falsify the expressions which
indicate the internal feelings! Thus conscious guilt shrinks from
detection, innocence declares its confidence, and hope anticipates
with bright expectation."

_Observation._ The fifth pair of nerves (fig. 126) is distributed to
the parts of the face on which the seventh pair ramifies. The former
serves for sensation, the latter for motion. Thus, when the seventh
pair of nerves is divided, or its functions destroyed by disease, the
side affected loses all power of expression, though sensation remains
unaffected. On the contrary, if we divide the fifth pair, sensation is
entirely destroyed, while expression remains.

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789. Are they also the instruments of expression, either of joy or
grief? 790. What is said in reference to the seventh pair of nerves?
Where is the fifth pair of nerves distributed?

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791. 5th. _The sympathetic nerve._ This nerve confers vitality on all
the important portions of the system. It exerts a controlling
influence over the involuntary functions of digestion, absorption,
secretion, circulation, and nutrition. Every portion of the body is,
to a certain extent, under its influence, as filaments from this
system of nerves accompany the blood-vessels throughout their course.

792. An important use of the sympathetic nerve is to form a
communication of one part of the system with another, so that one
organ can take cognizance of the condition of every other, and act
accordingly. If, for example, disease seizes the brain, the stomach,
by its sympathetic connection, knows it; and as nourishment would add
to the disease, it refuses to receive food, and perhaps throws