 This rule-of-thumb cannot be used without care as it cannot be applied to vipers, which have a large number of small scales on the head.A careful check would also be needed to exclude known poisonous members of the Colubrid family such as "Rhabdophis".In South Asia, it is advisable to take the snake which has bitten a person, if it has been killed, and carry it along to the hospital for possible identification by medical staff using scale diagrams so that an informed decision can be taken them as to whether and which anti-venom is to be administered.