The Weigl typhus vaccine was made by the intrarectal inoculation of lice. Twelve-day-old lice were put in a clamp with their rears in the air. A very fine glass pipette was inserted into the anus and a tiny drop of fluid containing the typhus bacterium was pumped in. The intestines were harvested and ground up with phenol to make the vaccine. These processes needed people: injectors, who could infect up to two thousand lice per hour; dissectors, who could harvest three hundred guts per hour; and feeders to propagate the lice, kept in cages strapped to their legs.