1. Leeches

No. 1 on our list of animals that have improved human medicine, leeches have been used for thousands of years to save people’s lives. Today, medicinal leeches are used after severe trauma to help close wounds, reattach digits, and mend skin after plastic surgery.

While there are about 650 species of these freshwater worms, only one is approved by the Food and Drug Administration for medical purposes: Hirudo Medicinalis. These leeches have triple jaws with hundreds of sharp teeth that help them suck the blood they need to feed themselves. They also secrete anticoagulants, which help the blood flow.

If you have a reattached thumb, the doctors will do their best to fix the tendons, muscles, and arteries, but the little veins that bring blood back to the circulatory system are traumatized and damaged. The blood pools in the limb and has nowhere to go, so you put the leech on the reattached thumb to suck out the extra blood until those little veins redevelop.

Animals that have improved human medicine are really cool!