\Lung\, n. [OE. lunge, AS. lunge, pl. lungen; akin to D.
long, G. lunge, Icel. & Sw. lunga, Dan. lunge, all prob. from
the root of E. light. ? See {Light} not heavy.] (Anat.)
An organ for a["e]rial respiration; -- commonly in the
plural.
      My lungs began to crow like chanticleer. --Shak.
Note: In all air-breathing vertebrates the lungs are
      developed from the ventral wall of the esophagus as a
      pouch which divides into two sacs. In amphibians and
      many reptiles the lungs retain very nearly this
      primitive saclike character, but in the higher forms
      the connection with the esophagus becomes elongated
      into the windpipe and the inner walls of the sacs
      become more and more divided, until, in the mammals,
      the air spaces become minutely divided into tubes
      ending in small air cells, in the walls of which the
      blood circulates in a fine network of capillaries. In
      mammals the lungs are more or less divided into lobes,
      and each lung occupies a separate cavity in the thorax.
      See {Respiration}.
{Lung fever} (Med.), pneumonia.
{Lung flower} (Bot.), a species of gentian ({G.
   Pneumonanthe}).
{Lung lichen} (Bot.), tree lungwort. See under {Lungwort}.
{Lung sac} (Zo["o]l.), one of the breathing organs of spiders
   and snails.