mortality in excess of 20 percent was expected and endured. Successive expeditions into the interior ended in disaster. In Laird's 1831 expedition up the Niger River, 40 of the 49 European expedition members died, most of them from "fevers." In a second expedition of 1841, 130 of 145 expedition members had been ill and 40 of these had died. It was noted that indigenous Africans serving on the e...