Catechu, an extract of the inner wood of the acacia catechu, a small tree which grows abundantly in the East Indies. The drug had long been in use before its origin was discovered. It is prepared by cutting off the exterior wood, and boiling the dark-colored chips of the interior of the trunk in water. The solution is then evaporated to the consistence of sirup, when it is dried in the sun in the form of flat cakes, or moulded by pouring it into earthen vessels. There are many varieties, some of which probably never reach this country. That common in our markets is the preparation above described, and is imported from Calcutta.
The pale catechu of the British pharmacopoeia, or gambir, is probably the substance formerly called terra japonica, and is the product of another tree, the uncaria gambir, of the family rubiaceae. Catechu contains-from 33 to 55 per cent, of that variety of tannic acid which precipitates the persalts of iron of a greenish black. Catechuic acid, in some respects resembling gallic acid, is found both in the dark and pale catechu. Catechu is used in dyeing and tanning under the name of cutch. It is used in medicine, in substance and tincture, as an astringent. It is said to be slightly tonic.