This text reconstructs everyday routines at the Oswaldo Cruz Institute in the early twentieth century based on statements from staff at that time. As Antonil wrote in 1711, “Slaves are the hands and feet of the sugar-mill owner.” The researchers’ assistants fulfilled a similar role in the laboratories; their work ranged from unskilled tasks to extremely delicate scientific research that today requires specialized training. These early technicians, many recruited as boys in the institution’s workshops, acquired their skills empirically. While the institute carried out modern activities, labor relations there still bore the marks of an agrarian and patriarchal society that had only recently abandoned slavery.