This paper explores the practical boundaries and linkages between modern and traditional medicine within a Tanzanian hospital. Despite the biomedical orientation of hospital protocols, diagnostic procedures, and treatment regimes, clinical practitioners often find it necessary to (unofficially) negotiate the presence of non-biomedical agents in medical practice. Drawing on ethnographic fieldwork in the Newala District Hospital, I examine the ways in which nurses and nurse-aides come to feel accountable to the harmful devils and potent jealous, which are the agents of locally older genealogies of medicine. At times, these clinical staff turn a blind eye when a relative brings in “traditional medicines” for a patient, withhold comment and sanction when a patient leaves in the hospital in the middle of the day to see a traditional healer, and tell patients or their families that hospital medicine will not work, as well as explicitly suggest that a patient go to see a particular traditional healer. I argue that such practices do not work to establish commensurability between “scientific” and “indigenous” realms of knowledge and practice, as much as they work to productively mediate the incommensurablities of biomedicine. Through this analysis, this paper brings the insights of studies on the difference in biomedicine together with literature concerning health and healing in Africa. Nurses and nurses’ aides are attending to bodies and afflictions that have no scientific existence. In these forms of referral and relationship nurses can potentially take on new forms of expertise. Furthermore, they are positioned to establish new forms of legitimacy, to render new natures existence in the hospital, and to alter the forms of nature that are important to the equivalencies of scientific sovereignties.