The hairs of the seed of Gossypium barbadense (G. herbaceum, U.S.P.) and other species, freed from adhering impurities and deprived of fatty matter,

Preparation. - It is made by boiling the raw cotton in a dilute alkaline solution, such as a 5 per cent. solution of caustic potash or soda. The alkali unites with the fatty matter of the cotton to form a soap, which is removed by repeated washings, in the course of which chlorinated lime and dilute hydrochloric acid are used as well as water.

Characters. - In white soft filaments, each consisting of an elongated tubular cell, and when examined under the microscope appearing as a flattened twisted band with slightly thickened rounded edges; inodorous and tasteless.

Test. - When thrown upon water it should immediately absorb the latter and sink, and the water should not acquire either an acid (no hydrochloric acid) or alkaline reaction.

Preparations.

B.P

Pyroxylin (Gun Cotton).

U.S.P

Pyroxylinum (Gun Cotton).

Uses. - Cotton wool is employed as a local application to the skin in cases of burns and erysipelas, to exclude external irritation and protect the part from cold. Cotton wool is also used to surround gouty or rheumatic joints.

A pledget of cotton wool placed in the ears tends to prevent ore-throat. The explanation of this seems to be that catarrh may result reflexly from irritation of the auricular branch of the vagus. (Cf. Rossbach's experiments, p. 252.)

When subjected to heat, so as to destroy any adherent germs, it is used in cultivation experiments on bacteria (p. 90) to plug the orifice of the test-tubes and prevent the accidental entrance of germs. With a somewhat similar object it has been used as a dressing to wounds, from which it excludes the germs which might cause pyaemia, erysipelas, etc. It may be impregnated with various antiseptics and deodorising substances, such as iodine, picric acid, salicylic acid, iodoform, or benzoic acid. Some of these form useful applications to the os uteri, to destroy foetor and induce healthy action. The dressing of wounds after operation by salicylic acid or iodoform wool has almost completely superseded the Listerian gauze dressing (p. 816).

Pyroxylin, B.P.; Pyroxylinum, U.S.P. Gun Cotton. Prepared by the action of sulphuric and nitric acids on cotton.

Test. - Readily soluble in a mixture of ether and rectified spirit: leaves no residue when exploded by heat.

Use. - To prepare collodium (collodion), B. and U.S.P.