What's the difference between i.e. and e.g.?
a magician's trick dating back to ancient Greece and Rome, involving the swallowing of a sword without bodily injury. Capuleius, in his Metamorphoseon, tells of seeing the trick in Athens, performed by a juggler on horseback. In reality, sword swallowing is not an illusion or trick. Those who practice it must first overcome their reflex gagging at objects touching the back part of their mouths. Long practice controls this reflex. The pharynx must also be conditioned. Objects introduced here cause much pain, and only after several trials can they be passed without great discomfort. The stomach is conditioned in a similar manner. Sword swallowers employ slightly varying methods. While one may swallow a sword without using any intermediate apparatus, such as a gutta-percha tip, another will take this precaution. The majority of sword swallowers employ a guiding tube which they have previously ingested, and hence their performances are less dangerous. The tube is 45-50 centimetres (17.7-19.7 inches) long and is made of very thin metal. With a width of 25 millimetres (a little less than an inch), the tube permits easy entry of flat-bladed swords. Exhibits of sword swallowing, beyond their entertainment value, have helped to further medicine by demonstrating to physicians that the pharynx could be habituated to contact, thus making experimentation and exploration of the involved organs possible