Toads

Roll up! Roll up! Buy your toad oil here!

Street performances are a common feature of samurai dramas on TV. On their travels around the country, the ninja would frequently disguise themselves as street performers and peddlers, of which peddlers of toad oil were some of the more famous. Toad oil may have been a highly implausible medicine, but the fact that it was adopted by the ninja suggests that there must have been some scientific basis.

The fluid secreted by toads contains a chemical that contracts the blood vessels. It would therefore have contracted the blood vessels at the site of a wound, and so toad oil could not be said to have been entirely without effect.