ence of an excess of alcohol is an advantage, as it prevents the
rapid evaporation of the ether. Under the microscope, the film produced
by collodion of good quality appears translucent and colourless. To
preserve collodion it should be kept cool and out of the action of the
light; iodized collodion that has been discoloured by the development of
free iodine may be purified by the immersion in it of a strip of silver
foil. For the iodizing of collodion, ammonium bromide and iodide, and
the iodides of calcium and cadmium are the agents employed (see
PHOTOGRAPHY). Collodion is used in surgery since, when painted on the
skin, it rapidly dries and covers the skin with a thin film which
contracts as it dries and therefore affords both pressure and
protection. Flexible collodion, containing Canada balsam and castor oil,
does not crack, but, on the other hand, does not contract. It is
therefore of less value. Collodion is applied to small aseptic wounds,
to small-pox pustules, and occasionally to the end of the urethra in
boys in order to prevent nocturnal incontinence. Collodion and crystals
of carbolic acid, taken in equal parts, are useful in relieving
toothache due to the presence of a carious cavity. _Vesicating_ or
_Blistering Collodion_ contains cantharidin as one of its constituents.
The styptic colloid of Richardson is a strong solution of tannin in
gun-cotton collodion. Similarly collodion may be impregnated with
salicylic acid, carbolic acid, iodine and other substances. Small
balloons are manufactured from collodion by coating the interior of
glass globes with the liquid; the film when dry is removed from the
glass by applying suction to the mouth of the vessel. M. E. Gripon found
(_Compt. rend._, 1875) that collodion membranes, like glass, reflect
light and polarize it both by refraction and reflection; they also
transmit a very much larger proportion of radiant heat, for the study of
which they are preferable to mica.

COLLOT D'HERBOIS, JEAN MARIE (1750-1796), French revolutionist, was a
Parisian by birth and an actor by profession. After figuring for some
years at the principal provincial theatres of France and Holland, he
became director of the playhouse at Geneva. He had from the first a
share in the revolutionary tumult; but it was not until 1791 that he
became a figure of importance. Then, however, by the publication of
_L'Almanach du Pere Gerard_,[1] a little book setting forth, in homely
style, the a