In James Joyce's "Ulysses," the hero Stephen Dedalus imagines making a telephone call to Eden using an umbilical cord as a cable. The humor of the scene derives from the wry disregard that most Westerners have for this most curious of temporary appendages, this ultimate reason for the belly-button.
(Also, of course, there's the ironic observation which is sometimes made, that Eden's human inhabitants presumably didn't have umbilical cords . . . )
If the bulk of Joyce's readers were Japanese, however, and had a more serious "attachment" to this bundle of tissue, would the scene be quite so comic? So attached are the Japanese to their umbilical cords that many never relinquish them. That's right, they still have them! Well, in a box, that is.