.

Be very careful to whom you trust one of these keys of the side-door.
The fact of possessing one renders those even who are dear to you very
terrible at times. You can keep the world out from your front-door, or
receive visitors only when you are ready for them; but those of your own
flesh and blood, or of certain grades of intimacy, can come in at the
side-door, if they will, at any hour and in any mood. Some of them have
a scale of your whole nervous system, and can play all the gamut of your
sensibilities in semitones,--touching the naked nerve-pulps as a pianist
strikes the keys of his instrument. I am satisfied that there are as
great masters of this nerve-playing as Vieuxtemps or Thalberg in their
lines of performance. Married life is the school in which the most
accomplished artists in this department are found. A delicate woman
is the best instrument; she has such a magnificent compass of
sensibilities! From the deep inward moan which follows pressure on the
great nerves of right, to the sharp cry as the filaments of taste are
struck with a crashing sweep, is a range which no other instrument
possesses. A few exercises on it dally at home fit a man wonderfully for
his habitual labors, and refresh him immensely as he returns from them.
No stranger can get a great many notes of torture out of a human soul;
it takes one that knows it well,--parent, child, brother, sister,
intimate. Be very careful to whom you give a side-door key; too many
have them already.

----You remember the old story of the tender-hearted man, who placed a
frozen viper in his bosom, and was stung by it when it became thawed? If
we take a cold-blooded creature into our bosom, better that it should
sting us and we should die than that its chill should slowly steal into
our hearts; warm it we never can! I have seen faces of women that were
fair to look upon, yet one could see that the icicles were forming
round these women's hearts. I knew what freezing image lay on the white
breasts beneath the laces!

A very simple _intellectual_ mechanism answers the necessities of
friendship, and even of the most intimate relations of life. If a watch
tells us the hour and the minute, we can be content to carry it about
with us for a life-time, though it has no second-hand, and is not
a repeater, nor a musical watch,--though it is not enamelled nor
jewelled,--in short, though it has little beyond the wheels required
for a trustworthy instrument, added