“Naturally, everyone would like to get their hands on kuru brains,” wrote D. Carleton Gajdusek in 1957. A young medical scientist, Gajdusek was writing from his bush laboratory in the eastern highlands of New Guinea, and he had in mind the competition among pathologists in Melbourne, Australia, and Bethesda, Maryland, for the valuable specimens. But he may also have considered his own recent transactions with the Fore people, afflicted with what he thought was the disease of kuru, and on whose hospitality he was then relying. Blood and brains, the germinal objects of his field research, were richly entangled in local community relations and global scientific networks; they could convey one meaning to the Fore, another to Gajdusek, and yet another to laboratory workers in Australia and the United States. These objects could be exchanged as gifts or commodities in different circumstances, or on the same occasion the different parties might confuse gift exchange with commodity transaction. At times, the scientist would try to obtain goods through barter, or even to appropriate them; and, then again, he might find that what he wanted was out of circulation altogether. In the field, Gajdusek had become enmeshed in a complex and fragile web of relationships with the Fore in order to acquire specimens that, through further exchanges with senior colleagues, might yet make his scientific reputation.