Poison \Poi"son\, n. [F. poison, in Old French also, a
         potion,
   fr. L. potio a drink, draught, potion, a
         poisonous draught,
   fr. potare to drink. See Potable, and cf.
         Potion.]
   1. Any agent
         which, when introduced into the
         animal organism,
      is capable of producing a morbid,
         noxious, or deadly
      effect upon it; as, morphine is a
         deadly poison; the
      poison of pestilential diseases.

              [1913 Webster]

   2. That which taints or destroys
         moral purity or health; as,
      the poison of evil
         example; the poison of sin.
      [1913 Webster]

  
         Poison ash. (Bot.)
 
             (a) A tree of the genus Amyris
         (Amyris
         balsamifera)
          found in the West Indies, from the trunk of which a
          black liquor distills, supposed to have poisonous
          qualities.
      (b) The poison sumac (Rhus venenata).
         [U. S.]

   Poison
         dogwood (Bot.), poison sumac.

  
         Poison fang (Zool.),
         one of the superior maxillary teeth
         of
      some species of serpents, which, besides having
         the cavity
      for the pulp, is either perforated or
         grooved by a
      longitudinal canal, at the lower end of
         which the duct of
      the poison gland terminates. See
         Illust. under Fang.

  
         Poison gland
         (Biol.), a gland,
         in animals or plants, which
      secretes an acrid or
         venomous matter, that is conveyed
      along an organ
         capable of inflicting a wound.

   Poison hemlock
         (Bot.), a poisonous umbelliferous plant
      ({Conium
         maculatum}). See Hemlock.

   Poison ivy
         (Bot.), a
         poisonous climbing plant (formerly
      {Rhus
         Toxicodendron}, or Rhus radicans, now classified
      as
         Toxicodendron
         radicans) of North America. It is
     
         common as a climbing vine, especially found on tree
     
         trunks, or walls, or as a low, spreading vine or as a
     
         shrub. As a low vine it grows well in lightly shaded
     
         areas, recognizable by growing in clusters of three
     
         leaves. Its leaves are trifoliate, rhombic-ovate, and
     
         variously notched. Its form varies slightly from location
 
             to location, leading to some speculation that it may
  
            consist of more than one species. Many people are
         poisoned
      by it, though some appear resistant to its
         effects.
      Touching the leaves may leave a residue of
         an oil on the
      skin, and if not washed off quickly,
         sensitive areas of
      skin become reddened and develop
         multiple small blisters,
      lasting for several days to
         several weeks, and causing a
      persistent itch. The
         toxic reaction is due to an oil,
      present in all parts
         of the plant except the pollen,
      called urushiol,
         the active component of which is the
      compound
         pentadecylacatechol
         (according to [a

     
         href="http:]/www.jaxmed.com/articles/Diseases/poison_ivy_dermatitis.htm">Charles

              H. Booras). See Poison sumac. It is related to
         poison oak, and is
         also called mercury.


          
         Poison nut. (Bot.)
 
             (a) Nux vomica.
      (b) The
         tree which yields this seed (Strychnos
         Nuxvomica). It is found on the Malabar and Coromandel
          coasts.

   Poison
         oak (Bot.), a dermatitis-producing
         plant often
      lumped together with the poison ivy
         (Toxicodendron radicans) in common terminology,
         but
         more properly
      distinguished as the more shrubby
         Toxicodendron quercifolium (syn.
         {Toxicodendron
         diversilobum}), common
      in California and Oregon.
         Opinion varies as to whether the
      poison oak and
         poison ivy are only variants of a single
      species. See
         poison ivy,
         above.

   Poison
         sac. (Zool.) Same as
         Poison gland,
         above. See
      Illust. under Fang.

 
          Poison sumac
         (Bot.), a poisonous shrub formerly
         considered
      to be of the genus Rhus ({Rhus
         venenata}), but now
      classified as {Toxicodendron
         vernix}; -- also called
      poison ash, {poison
         dogwood}, and poison
         elder. It has
      pinnate leaves
         on graceful and slender common petioles,
      and usually
         grows in swampy places. Both this plant and
      the
         poison ivy (Toxicodendron radicans, formerly {Rhus
     
         Toxicodendron}) have clusters of smooth greenish white
    
          berries, while the red-fruited species of this genus are
 
             harmless. The tree (Rhus vernicifera) which yields
         the
      celebrated Japan lacquer is almost identical with
         the
      poison sumac, and is also very poisonous. The
         juice of the
      poison sumac also forms a lacquer
         similar to that of
      Japan.
      [1913 Webster
         +PJC]

   Syn: Venom; virus; bane; pest; malignity.

  
         Usage: Poison, Venom.
         Poison usually denotes something
          received into the system by the mouth, breath, etc.
          Venom is something discharged from animals and
          received by means of a wound, as by the bite or sting
          of serpents, scorpions, etc. Hence, venom specifically
          implies some malignity of nature or purpose.
          [1913 Webster]