The cousso tree (Hagenia abyssinica) is native to Abyssinia, where it is generally planted about the villages on the high tablelands, from 3,000 to 8,000 feet above the sea level. Bruce (105) observed its uses, 1768-1773, during his expedition to discover the sources of the Nile, and Willdenow (385), 1799, described it under the name Hagenia. Its use as a vermifuge was derived from Abyssinian domestic practice, the decoction being used for this purpose. In early European record an extraordinarily high price was asked for this substance. It was introduced in 1850 by a Frenchman, who demanded in the neighborhood of $9 per ounce. This led to its importation in quantities, when the value soon fell to a normal standard.
The History of the Vegetable Drugs of the U.S.P., 1911, was written by John Uri Lloyd.