It's said that ninja possessed a thorough knowledge of medicinal plants. They grew a personal supply of plants to be used as remedies for illness or injury, or to be mixed to make poisons or sleeping potions that could be carried on their person and used for their spying activities. In an era when drug manufacturing skills and technology were not widespread, peddlers travelled the country on foot to sell their medicines. Ninja used this to their advantage, impersonating medicine hawkers so they could pass easily all around the country without raising the suspicions of the locals, carrying out their spying activities at the same time as earning a living from selling their goods. In some ninja museums there are books displayed that were passed down within clans, detailing various compounds and directions for use. Koga - famous as a 'ninja town' - is home to many pharmaceutical companies these days as a legacy of this; so much so that it is also known as 'medicine town'.
