Nicole Maxwell comes from a long line of pioneers -- a family of early colonists and settlers of the American West. That may explain why she--the California oil man's daughter, trained in biology at Harvard and ballet in Paris--at age 40 divorced a U.S. Air Force brigadier general at the end of World War II and began a journey through the Amazon jungle that has lasted more than 30 years.

"I suppose I am a slow traveler," Maxwell says.

Nicole Maxwell is not an ordinary traveler. On a largely solitary adventure among the Indian tribes of the western Amazon, she has devoted close to half her life investigating and recording the elusive and rapidly vanishing secrets of native plant medicine.

Maxwell has collected and studied nearly 600 different medicinal plant specimens. Among the most important, she believes, are herbal remedies used by the region's native population to stop bleeding, painlessly extract teeth, dissolve kidney stones and treat serious burns. Perhaps most spectacularly, she has recovered and identified a plant trusted by native women as a potent organic contraceptive, widely used to alter a woman's fertility for up to eight years per dose.

Now 76, Maxwell lives alone in Iquitos, a Peruvian boom town on the Amazon River. She is a small woman with delicate features and arresting energy. Dressed in blue jeans and a denim shirt, she smokes Camel no-filters from a cigarette holder. With a combination of natural elegance, self-conscious humor and rugged individualism, she has that rare blend of qualities once described as "character."

Maxwell says that when she first came to the jungle in 1948, she had neither great faith nor special interest in the unconventional practices of native medicine. "I'd heard of plant medicine before, but of course I'd gone to medical school," she says. She became interested in the subject while on a jungle expedition a few years later, when she stumbled onto her machete. Miles from the nearest hospital, a deep gash in her arm was treated with a liquid concoction made by an Indian guide from the sap of a local tree. "The bleeding stopped after a few minutes," she recalls, "to my very great astonishment."

Working as a journalist at the time of the incident, Maxwell decided to look into the uses of medicinal plants "by poking around in a very unprofessional way."

What she learned led her, in 1958, to persuade a large American pharmaceutical company to finance a one-woman expedition into the jungle to collect samples of herbal remedies. She set off by boat from Iquitos with a plant press, transistor radios, some camera equipment and a sack of trading goods, which included an assortment of 20 glass eyeballs.

While the company had been, at best, wary about the prospects of learning anything from Indian medicine, the idea of a white woman traveling alone in some of the least-known parts of the Amazon raised eyebrows even in Iquitos. "You're crazy," she remembers being told by one local boatman. "They'll kill you."

She returned from the jungle 10 months later, weary and broke but still in one piece. Through special friendships, patient negotiation and occasionally hard bargaining with the native tribes the expedition had yielded some prize specimens. As on subsequent trips into the remote Amazon, she found the Indians she met receptive to respectful queries about their special cures.

"Perhaps because I am a woman and traveling alone," she says, "I have been fortunate enough to break through reserves and taboos of a number of tribes. A woman presents no threat. It is quite certain that she will not kill the men or press them into serfdom, and she will obviously not attempt to seduce their wives."

Being a woman, she believes, also has permitted her access to the very closely guarded "woman's magic" of controlling fertility.

A contraceptive plant widely known as piripiri ("good medicine, all women take," she was informed by an Indian friend) was among the samples that she handed over to the pharmaceutical company upon her return to New York. The collection also included specimens of the incara tree, used to painlessly extract teeth, of the chanca piedra leaf, used to expel gall and kidney stones, of another leaf used to treat burns and another that worked as a powerful antihangover potion. The company gratefully accepted the specimens, and promised to inform Maxwell of the results of its initial laboratory study.

It never did, Maxwell says. She believes that the plants were lost or simply ignored, and that her trip had been financed as part of a publicity stunt.

During the last 20 years, which have included six other investigative expeditions, Maxwell has continued to fight prevailing skepticism toward the value of "primitive" medicine. She has written a book about her adventures, "Witch Doctor's Apprentice," first published in 1961 and reissued in 1975 in an updated version. It is a lively and poignant chronicle of her affair with the jungle and respect for the native knowledge that she describes as "the strange combination of superstition and wisdom, ignorance and insight, which always, as much as I have seen it, awes and astonishes me."

Maxwell says that bringing native medicine to the attention of modern science "is what I'm for." Without money to mount further expeditions, she has turned to classifying and writing about materials already collected in field notes.

"I'm absolutely sure," she says, "that of the hundreds of plants I've collected, there are at least 30 that can cure things that our modern medicine can't.

"It is my belief that these should be studied before the acculturation process already resulting from the swift advance of modern civilization causes them to be forgotten."