Snake venom is highly modified saliva containing zootoxins that facilitates the immobilization and digestion of prey, and defends against a threat. It is injected by unique fangs after a bite but some species are also able to spit.The glands that secrete the zootoxins are a modification of the parotid salivary gland found in other vertebrates and are usually situated on each side of the head, below and behind the eye and encapsulated in a muscular sheath.