Medical analysis of sword swallowing.

Sword swallowing is not an illusion but, unlike in normal swallowing (when the tongue pushes the bolus up against the palate with the neck in a neutral position), the back of the tongue is pushed forwards and the neck hyperextended. Repeated practice enables suppression of the gag reflex. The pharynx is thrust forward and the cricopharyngeus relaxed. The sword may be passed after deep inspiration with the pharynx filled with air -- one practitioner describes "sucking in" rather than swallowing the sword. Once past the pharynx, the lubricated sword is swiftly passed, straightening the distensible and elastic oesophagus. Gravity helps, for the performer is always upright.

The sword passes within millimetres of the heart, aorta, and other vitals but, surprisingly, few deaths related to sword swallowing have been described.

Here are some related x-ray images. (Via Boing Boing.)