linen manufacture.  The details of the process are somewhat different.  The jute is commonly fermented in tanks of stagnant water, although sometimes it is allowed to soak in river water for a sufficient length of time to produce the softening.  After the fermentation is thus started the jute fibre is separated from the wood, and is of a sufficient flexibility and toughness to be woven into sacking, carpets, curtains, table covers, and other coarse cloth.

Practically the same method is used in separating the tough fibres of the hemp.  The hemp plant contains some long flexible fibres with others of no value, and bacterial fermentation is relied upon to soften the tissues so that they may be separated.

Cocoanut fibre, a somewhat similar material is obtained from the husk of the cocoanut by the same means.  The unripened husk is allowed to steep and ferment in water for a long time, six months or a year being required.  By this time the husk has become so softened that it can be beaten until the fibres separate and can be removed.  They are subsequently made into a number of coarse articles, especially valuable for their toughness.  Door mats, brushes, ships’ fenders, etc., are illustrations of the sort of articles made from them.

In each of these processes the fermentation must have a tendency to soften the desired fibres as well as the connecting substance.  Putrefaction attacks all kinds of vegetable tissue, and if this “retting” continues too long the desired fibre is decidedly injured by the softening effect of the fermentation.  It is quite probable that, even as commonly carried on, the fermentation has some slight injurious effect upon the fibre, and that if some purely mechanical means could be devised for separating the fibre from the wood it would produce a better material.  But such mechanical means has not been devised, and at present a putrefactive fermentation appears to be the only practical method of separating the fibres.

Sponges.—­A somewhat similar use is made of bacteria in the commercial preparation of sponges.  The sponge of commerce is simply the fibrous skeleton of a marine animal.  When it is alive this skeleton is completely filled with the softer parts of the animal, and to fit the sponge for use this softer organic material must be got rid of.  It is easily accomplished by rotting.  The fresh sponges are allowed to stand in the warm sun and very rapidly decay.  Bacteria make their way into the sponge and thoroughly decompose the soft tissues.  After a short putrefaction of this sort the softened organic matter can be easily washed out of the skeleton and leave the clean fibre ready for market.