Its quaint but don't use it. Current medical practice is to use a constrictor bandage only(wrap the entire limb tightly with a bandage, preferebly elastic), keep the victim calm (how?) and get them to a medical centre ASAP. In Australia they have kits that detect which species of snake performed the deed from spillage from the wound so it is best not to wash the wound.
Older remedies can prove dangerous. Sucking on the wound to remove the poison could introduce the poison into the helpers bloodstream via cuts and tooth cavities while cutting the wound to draw out the poison can simply spread it to other vessels.
If you disagree with what I have said here, immediatly post a reply. I'ld rather have a bruised ego than be responsable for spreading dangerous misinformation.