context: A pharmaceutical company sends biochemist Dr. Rae Crane into the Amazonian Rainforest to check on Dr. Robert Campbell after he cuts off outside contact, his wife and research partner having left him.
  Crane is bringing supplies (everything from golf balls to a gas chromatograph), but Campbell is upset that he was not given the research partner he had requested. He tries to send her home but Crane dismisses Campbell's attempts to spurn her, as her job is to evaluate whether the company should continue funding his research.Campbell reveals to her shock that he has found a cure for cancer, but that subsequent attempts to recreate the formula have failed.They wondered why peak 37 is not seen in the chromatograph. With the initial successful serum running dangerously low, Campbell has isolated a mysterious chemical compound connected to a species of flower and with Crane's help is determined to find its source.Time is of the essence, as a nearby logging company is building a road that is headed straight for the village. Campbell refuses to ask the pharmaceutical company for help, fearing that they would send in more researchers from the outside world, unintentionally wiping out the native population with exposure to foreign diseases.
  Campbell reveals that a similar event previously had happened when he was conducting field research for a new pain reliever. He feels guilt at causing the death of an entire village, revealing that his wife left because he would not let her forgive him.A small boy shows symptoms of malignant neoplasms that will kill him if not treated. The boy's father takes him to find the village's previous medicine man, from whom Campbell had originally learned about the existence of the flowers. Campbell's presence caused the medicine man to feel overshadowed and leave. He is reluctant to face the medicine man again, but Crane convinces him they must.Campbell first rescues Crane from a fall, then locates the medicine man. Campbell is forced to fight him in an attempt to soothe the medicine man's hurt pride and gain information. Unhappily, the medicine man reveals that the flowers have no "juju." As a consolation, the father and ill son do agree to return.
  Back at the village, Crane refuses to let Campbell use the last of the serum on the boy until they have managed to synthesize more of it. Faced with the prospect of letting a child die, Crane's conscience overcomes her hesitation. She saves the boy with the last of the working serum.The next morning, the boy is better but the village is in tumult. The logging road has nearly reached it. Campbell appeals to the company's workers to halt construction until he can conclude his research, but they refuse to stop the bulldozers without more conclusive proof.In desperation after their new samples fail to reveal the missing compound, Crane runs the chromatograph one more time. She accidentally discovers that the source of the cure is not the flower but a species of rare, indigenous ant.Campbell rushes to stop the construction. A fight results in a bulldozer catching fire, burning down the village and the research post along with many acres of rain forest.The next day, Crane promises to send Campbell new equipment and his originally requested research assistant. She is about to return home when she meets the old medicine man. He symbolically passes on his mantle to Campbell, and she accepts an invitation to continue working with Campbell in exchange for co-credit for the discovery.
question: What is the source of the cure?
answer: A species of rare, indigenous ant.