How do you make antivenom?

To make antivenom, you take advantage of the natural immune system of a vertebrate animal. This could be a horse, a sheep, a goat, a donkey, a rabbit, a mouse, a shark, a human being: all of these (and more) have been used for the purpose in the past. You give that animal a carefully crafted immunization, followed by a series of booster shots, kind of like when we give tetanus shots to people. After a while, your animal is making a whole lot antibodies against whatever you used to immunize it (part of the body’s way of protecting itself against toxins). The animal can then serve as a blood donor from time to time, and the antibodies can be harvested and purified into a treatment for snakebite or scorpion sting. (It’s really not a bad career choice for a domestic animal.)