What is a gorilla? Just 160 years ago, no European (or North American) had ever seen one, though there were many reports of "hellish dream creatures" living in the West African jungles. In "Between Man and Beast" (Doubleday, 331 pages, $26.95), Monte Reel follows the life of Paul du Chaillu, an unlikely explorer/scientist whose accounts of his upriver travels in Gabon ignited widespread scientific controversy. This is a lively and intriguing biography of the restless adventurer who first sees, studies and takes specimens of gorillas.

Du Chaillu was the son of a French river trader and (most likely) a black native woman, a parentage the young man never acknowledged. Chance brought him to a pair of American missionaries living at the mouth of the Gabon River; their kindness created in him a strong sense of Christian piety and filial devotion. When the missionaries returned to the United States, Du Chaillu accompanied them, delighting in the nation's freedoms.

The story truly begins, though, when Du Chaillu returned to Africa in 1855 to collect specimens for American museums, especially those of the secretive njena (gorillas) he had heard about from tribesmen. Here, Reel allows us to accompany Du Chaillu into equatorial heat, malarial swamps and the territories of fearful tribes. The diminutive explorer (5 feet tall) possessed a remarkable facility for picking up new languages and a tireless constitution. Moreover, he took enormous prophylactic doses of quinine (which, Reel explains, can contribute to feelings of "spiritual exceptionalism"). When Du Chaillu returned to the United States, he had with him a number of carefully preserved gorilla skins.

Yet upon his return, Du Chaillu encountered the scorn of the American scientific community, which regarded him as a fraud. His French-inflected English was sensational (the quinine?) rather than scientific. His data lacked precision. His patrons refused to honor their financial debts to him.

Failing even as a New York sideshow proprietor (just down the street from P.T. Barnum), Du Chaillu sailed to England, where almost immediately he was taken up and acclaimed by the country's most distinguished zoologists. "Explorations and Adventures in Equatorial Africa," his travelogue, became the best-selling book of 1858. Reel does an excellent job of chronicling Du Chaillu's misery in America and his A-list celebrity-hood in England.

While Du Chaillu's adventures on three continents are fascinating in themselves, Reel points out that the gorilla phenomenon fed ideological debates on both sides of the Atlantic. Du Chaillu's lectures, for instance, took place just as Britain's intelligentsia was encountering Darwin's ideas on evolution. (As a missionary-taught Christian, Du Chaillu found himself championed by the anti-Darwinists.) Meanwhile, in the Uninted States, questions about the gorilla's relationship to humans added to the ever-present debates about race relations. In the national mania concerning Caucasian purity, gorilla became "the ultimate dehumanizing epithet for blacks."

Reel's title offers playful homage to the melodramatic prose about gorillas that has been so much a part of popular culture (think King Kong!). His prose, by contrast is direct, informative and thoroughly engrossing.

Tom Zelman teaches English at the College of St. Scholastica in Duluth.