The husk on the outside of the walnut contains most of the jugalone. That's the green-to-black part on the outside of the fruit. If you've bought whole walnuts

The husk on the outside of the walnut contains most of the jugalone. That's the green-to-black part on the outside of the fruit. If you've bought whole walnuts (dry, brown, wrinkly), but never seen them in the wild, you've never seen this part. The horses and pigs get sick because they only eat the husk, they can't crack the shell to get at the nutritious part. The meat inside of the shell is safe. Reference: https://extension.illinois.edu/blogs/extensions-greatest-hits/1999-10-02-preparing-black-walnuts-eating https://extension.illinois.edu/blogs/extensions-greatest-hit...