From about July 1942 to about September 1943, experiments to investigate the effectiveness of sulfonamide, a synthetic antimicrobial agent, were conducted at Ravensbrück.[15] Wounds inflicted on the subjects were infected with bacteria such as Streptococcus, Clostridium perfringens (the causative agent in gas gangrene) and Clostridium tetani, the causative agent in tetanus.[16] Circulation of blood was interrupted by tying off blood vessels at both ends of the wound to create a condition similar to that of a battlefield wound. Infection was aggravated by forcing wood shavings and ground glass into the wounds.