Interesting fact:

In the original 1973 film, one of the actor's had to tackle a real rattlesnake, though thankfully one milked of its venom. The actor in question was supposed to be bitten by the creature, so his arm was padded with cotton and leather. But the pesky snake still managed to work around all that leather and bite the man on an unprotected part of his arm anyway! I imagine they left it at one take...