Source : Webster's Revised Unabridged Dictionary (1913)

Lactic \Lac"tic\, a. [L. lac, lactis, milk: cf. F. lactique. See
   {Lacteal}, and cf. {Galactic}.] (Physiol. Chem.)
   Of or pertaining to milk; procured from sour milk or whey;
   as, lactic acid; lactic fermentation, etc.

   {Lactic acid} (Physiol. Chem.), a sirupy, colorless fluid,
      soluble in water, with an intensely sour taste and strong
      acid reaction. There are at least three isomeric
      modifications all having the formula {C3H6O3}. Sarcolactic
      or paralactic acid occurs chiefly in dead muscle tissue,
      while ordinary lactic acid results from fermentation. The
      two acids are alike in having the same constitution
      (expressed by the name ethylidene lactic acid), but the
      latter is optically inactive, while sarcolactic acid
      rotates the plane of polarization to the right. The third
      acid, ethylene lactic acid, accompanies sarcolactic acid
      in the juice of flesh, and is optically inactive.

   {Lactic ferment}, an organized ferment ({Bacterium lacticum
      or lactis}), which produces lactic fermentation,
      decomposing the sugar of milk into carbonic and lactic
      acids, the latter, of which renders the milk sour, and
      precipitates the casein, thus giving rise to the so-called
      spontaneous coagulation of milk.

   {Lactic fermentation}. See under {Fermentation}.



   2. A state of agitation or excitement, as of the intellect or
      the feelings.

            It puts the soul to fermentation and activity.
                                                  --Jer. Taylor.

            A univesal fermentation of human thought and faith.
                                                  --C. Kingsley.

   {Acetous, or Acetic}, {fermentation}, a form of oxidation in
      which alcohol is converted into vinegar or acetic acid by
      the agency of a specific fungus or ferment ({Mycoderma
      aceti}). The process involves two distinct reactions, in
      which the oxygen of the air is essential. An intermediate
      product, aldehyde, is formed in the first process. 1.
      C2H6O + O = H2O + C2H4O

   Note: Alcohol. Water. Aldehyde. 2. C2H4O + O = C2H4O2

   Note: Aldehyde. Acetic acid.

   {Alcoholic fermentation}, the fermentation which saccharine
      bodies undergo when brought in contact with the yeast
      plant or Torula. The sugar is converted, either directly
      or indirectly, into alcohol and carbonic acid, the rate of
      action being dependent on the rapidity with which the
      Torul[ae] develop.

   {Ammoniacal fermentation}, the conversion of the urea of the
      urine into ammonium carbonate, through the growth of the
      special urea ferment. CON2H4 + 2H2O = (NH4)2CO3

   Note: Urea. Water. Ammonium carbonate.

   Note: Whenever urine is exposed to the air in open vessels
         for several days it undergoes this alkaline
         fermentation.

   {Butyric fermentation}, the decomposition of various forms of
      organic matter, through the agency of a peculiar
      worm-shaped vibrio, with formation of more or less butyric
      acid. It is one of the many forms of fermentation that
      collectively constitute putrefaction. See {Lactic
      fermentation}.

   {Fermentation by an} {unorganized ferment or enzyme}.
      Fermentations of this class are purely chemical reactions,
      in which the ferment acts as a simple catalytic agent. Of
      this nature are the decomposition or inversion of cane
      sugar into levulose and dextrose by boiling with dilute
      acids, the conversion of starch into dextrin and sugar by
      similar treatment, the conversion of starch into like
      products by the action of diastase of malt or ptyalin of
      saliva, the conversion of albuminous food into peptones
      and other like products by the action of
      pepsin-hydrochloric acid of the gastric juice or by the
      ferment of the pancreatic juice.

   {Fermentation theory of disease} (Biol. & Med.), the theory
      that most if not all, infectious or zymotic disease are
      caused by the introduction into the organism of the living
      germs of ferments, or ferments already developed
      (organized ferments), by which processes of fermentation
      are set up injurious to health. See {Germ theory}.

   {Glycerin fermentation}, the fermentation which occurs on
      mixing a dilute solution of glycerin with a peculiar
      species of schizomycetes and some carbonate of lime, and
      other matter favorable to the growth of the plant, the
      glycerin being changed into butyric acid, caproic acid,
      butyl, and ethyl alcohol. With another form of bacterium
      ({Bacillus subtilis}) ethyl alcohol and butyric acid are
      mainly formed.

   {Lactic fermentation}, the transformation of milk sugar or
      other saccharine body into lactic acid, as in the souring
      of milk, through the agency of a special bacterium
      ({Bacterium lactis} of Lister). In this change the milk
      sugar, before assuming the form of lactic acid, presumably
      passes through the stage of glucose. C12H22O11.H2O =
      4C3H6O3

   Note: Hydrated milk sugar. Lactic acid.

   Note: In the lactic fermentation of dextrose or glucose, the
         lactic acid which is formed is very prone to undergo
         butyric fermentation after the manner indicated in the
         following equation: 2C3H6O3 (lactic acid) = C4H8O2
         (butyric acid) + 2CO2 (carbonic acid) + 2H2 (hydrogen
         gas).

   {Putrefactive fermentation}. See {Putrefaction}.