The Anti-Venom Effect

So he started injecting animals with small amounts of venom and they've become somewhat resistant to the venom. How has he then got the anti-venom? We'll get to that. So is he feeding people the horses? Here's the thing. He'd inject the horses with the venom and the horses would then produce antibodies to that venom. What are antibodies? I think they're like a little key, almost like a littleKey that goes into the keyhole on the virus or in this case the venom and binds to it and makes it basically inert, like useless.