Snake Eats Iguana

Cobras, vipers, and closely related species use venom to immobilize or kill their prey. The venom is modified saliva, delivered through fangs.:243 The fangs of 'advanced' venomous snakes like viperids and elapids are hollow to inject venom more effectively, while the fangs of rear-fanged snakes such as the boomslang merely have a groove on the posterior edge to channel venom into the wound. Snake venoms are often prey specific, their role in self-defense is secondary.:243 Venom, like all salivary secretions, is a predigestant that initiates the breakdown of food into soluble compounds, facilitating proper digestion. Even nonvenomous snake bites (like any animal bite) will cause tissue damage.:209
Certain birds, mammals, and other snakes such as kingsnakes that prey on venomous snakes have developed resistance and even immunity to certain venoms.:243 Venomous snakes include three families of snakes, and do not constitute a formal classification group used in taxonomy. The term poisonous snake is mostly incorrect; poison is inhaled or ingested, whereas venom is injected. There are, however, two exceptions—Rhabdophis sequesters toxins from the toads it eats, then secretes them from nuchal glands to ward off predators, and a small population of garter snakes in Oregon retains enough toxin in their liver from the newts they eat to be effectively poisonous to local small predators such as crows and foxes.
Snake venoms are complex mixtures of proteins, and are stored in poison glands at the back of the head. In all venomous snakes, these glands open through ducts into grooved or hollow teeth in the upper jaw.:243 These proteins can potentially be a mix of neurotoxins (which attack the nervous system), hemotoxins (which attack the circulatory system), cytotoxins, bungarotoxins and many other toxins that affect the body in different ways. Almost all snake venom contains hyaluronidase, an enzyme that ensures rapid diffusion of the venom.:243
Venomous snakes that use hemotoxins usually have the fangs that secrete the venom in the front of their mouths, making it easier for them to inject the venom into their victims. Some snakes that use neurotoxins, such as the mangrove snake, have their fangs located in the back of their mouths, with the fangs curled backwards. This makes it both difficult for the snake to use its venom and for scientists to milk them. Elapid snakes, however, such as cobras and kraits are proteroglyphous, possessing hollow fangs that cannot be erected toward the front of their mouths and cannot "stab" like a viper; they must actually bite the victim.:242