1 | Milk Venom Any good antivenom starts with its opposite. Herpetologists do the milking, forcing the snake to bite down on the lip of a jar so that venom drips from its fangs. Manufacturers buy individual snake venoms from suppliers and mix them together to create a supervenom.

2 | Inject Horse On the Ojo de Agua ranch in Puebla, horses live pleasant lives—except for the regular supervenom injections. Scientists start with just a few micrograms of the mixture and gradually increase the dose over six months. With every injection, the horse develops more antibodies capable of fighting off each of the venoms included in the mix.

3 | Draw Blood Every four weeks over the horse’s 25-year life, it receives a booster shot of supervenom to spur antibodies. About 10 days later, workers tap the horse’s jugular vein and draw 5 liters of blood.

4 | Separate Plasma The venom-targeting antibodies live in the horse’s plasma. Equine red blood cells sink to the bottom of a blood bag, leaving the plasma floating above. Technicians return the blood, minus plasma, to the horse to prevent anemia.

5 | Add Enzyme Doctors used to inject rattlesnake-bite victims with unprocessed horse anti­venom, which caused a reaction almost as unpleasant as the bite. Now scientists use the enzyme pepsin—found in stomach acid—to “digest” away everything but the antibodies.

6 | Dehydrate & Bottle A freeze dryer dehydrates the antibody into a powder. When doctors inject the antivenom into a victim, symptoms can subside in just hours, and bitees often walk out of the hospital just a day later.