Ink \Ink\, n. [OE. enke, inke, OF. enque, F. encre, L. encaustum
   the purple red ink with which the Roman emperors signed their
   edicts, Gr. ?, fr. ? burnt in, encaustic, fr. ? to burn in.
   See Encaustic, Caustic.]
   1. A fluid, or a viscous material or preparation of various
      kinds (commonly black or colored), used in writing or
      printing.
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            Make there a prick with ink.          --Chaucer.
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            Deformed monsters, foul and black as ink. --Spenser.
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   2. A pigment. See India ink, under India.
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   Note: Ordinarily, black ink is made from nutgalls and a
         solution of some salt of iron, and consists essentially
         of a tannate or gallate of iron; sometimes indigo
         sulphate, or other coloring matter, is added. Other
         black inks contain potassium chromate, and extract of
         logwood, salts of vanadium, etc. Blue ink is usually a
         solution of Prussian blue. Red ink was formerly made
         from carmine (cochineal), Brazil wood, etc., but
         potassium eosin is now used. Also red, blue, violet,
         and yellow inks are largely made from aniline dyes.
         Indelible ink is usually a weak solution of silver
         nitrate, but carbon in the form of lampblack or India
         ink, salts of molybdenum, vanadium, etc., are also
         used. Sympathetic inks may be made of milk, salts of
         cobalt, etc. See Sympathetic ink (below).
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   Copying ink, a peculiar ink used for writings of which
      copies by impression are to be taken.

   Ink bag (Zool.), an ink sac.

   Ink berry. (Bot.)
      (a) A shrub of the Holly family (Ilex glabra), found in
          sandy grounds along the coast from New England to
          Florida, and producing a small black berry.
      (b) The West Indian indigo berry. See Indigo.

   Ink plant (Bot.), a New Zealand shrub (Coriaria
      thymifolia), the berries of which yield a juice which
      forms an ink.

   Ink powder, a powder from which ink is made by solution.

   Ink sac (Zool.), an organ, found in most cephalopods,
      containing an inky fluid which can be ejected from a duct
      opening at the base of the siphon. The fluid serves to
      cloud the water, and enable these animals to escape from
      their enemies. See Illust. of Dibranchiata.

   Printer's ink, or Printing ink. See under Printing.

   Sympathetic ink, a writing fluid of such a nature that what
      is written remains invisible till the action of a reagent
      on the characters makes it visible.
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Sympathetic \Sym`pa*thet"ic\, a. [See Sympathy, and cf.
   Pathetic.]
   1. Inclined to sympathy; sympathizing.
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            Far wiser he, whose sympathetic mind
            Exults in all the good of all mankind. --Goldsmith.
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   2. Produced by, or expressive of, sympathy.
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            Ope the sacred source of sympathetic tears. --Gray.
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   3. (Physiol.)
      (a) Produced by sympathy; -- applied particularly to
          symptoms or affections. See Sympathy.
      (b) Of or relating to the sympathetic nervous system or
          some of its branches; produced by stimulation on the
          sympathetic nervious system or some part of it; as,
          the sympathetic saliva, a modified form of saliva,
          produced from some of the salivary glands by
          stimulation of a sympathetic nerve fiber.
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   Sympathetic ink. (Chem.) See under Ink.

   Sympathetic nerve (Anat.), any nerve of the sympathetic
      system; especially, the axial chain of ganglions and
      nerves belonging to the sympathetic system.

   Sympathetic powder (Alchemy), a kind of powder long
      supposed to be able to cure a wound if applied to the
      weapon that inflicted it, or even to a portion of the
      bloody clothes. --Dunglison.

   Sympathetic sounds (Physics), sounds produced from solid
      bodies by means of vibrations which have been communicated
      to them from some other sounding body, by means of the air
      or an intervening solid.

   Sympathetic system (Anat.), a system of nerves and nerve
      ganglions connected with the alimentary canal, the
      vascular system, and the glandular organs of most
      vertebrates, and controlling more or less their actions.
      The axial part of the system and its principal ganglions
      and nerves are situated in the body cavity and form a
      chain of ganglions on each side of the vertebral column
      connected with numerous other ganglions and nerve
      plexuses.
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