Myrabolams are mainly used in England and Austria, and give a nice light-colored leather, both upper and sole, although rarely used alone.  Their main use is for dyeing purposes.  They are indigenous to the East Indies.

Sumac is so well known that treating of it is superfluous.  Its use is very extensive, and it is a general favorite for light, fine leather, which is mostly used for colors.

Gambier—­Is in general use in England and to some extent in Germany.

Catechu.—­Obtained from India, resembles gambier greatly.  Its use is almost wholly confined to England.  It is also consumed by the silk manufacturers in preference to gambier, for weighting purposes.

PATHOLOGICAL.

We now leave the physiological class and take up those tanning materials included in the pathological class, or those of abnormal growth.

Galls.—­These are not consumed to any great extent at the present period, but formerly they were used quite extensively.  The galls are found upon the leaves of the oak or sumac, etc.  The direct cause of their growth is that a certain wasp (cynips galles) stings into the leaf and after depositing its egg, flies away.  The egg develops into a larva and then into a full-fledged wasp, boring its way out of the gall which has served as a protection and nourisher.  This accounts for the hole noticed in almost every gall.  The different varieties include Aleppo.  It is found upon the same trees as the valonia and contains 60 to 75 per cent. tannin; Istrian galls, 32 per cent. tannin; Persian, 28 to 29 per cent. tannin.  Chinese galls, giving 80 to 82 per cent. tannin, are the results of the sting of a louse, and make a very light-colored leather.  The dyers also use this material for coloring.

Knoppern—­Belongs to the family of galls, and is a most important factor of commerce in Austria.  The knopper is generally found on the acorn or leaf of the oak tree.  The greatest quantity is derived from the steel oak of Hungary.  The tannin contained varies from 27 to 33 per cent.  Knoppern are not being used so much now as formerly, and consequently the amount harvested lessens from year to year.  Its main use was and is in combination with valonia as layers for sole leather.  Valonia gives better weight results than knoppern, and is replacing knoppern more and more every year.  The combination of knoppern, valonia and myrabolams is also quite popular, and gives good results.  Knoppern are seldom used alone, being generally combined with some other tannin.  Austria is almost the only consumer at present, but Germany used it extensively formerly.

Bark and Wood Extracts—­Are becoming general favorites throughout Europe, partly because of their weight-giving qualities and partly as the transportation costs so little; they can be used to strengthen weak bark liquors.

Oak Extracts—­Are well liked, both wood and bark, and are used extensively.  Slavonia furnishes a great deal of it.