pakua and hsing yi tell you to stare at the fingernail so you can see around you...

http://www.asbweb.org/conferences/2006/pdfs/112.pdf

the Extensor Indicis is involved in the extension of the wrist and index finger, now if you google your map you will see it drawn as a bulge below the bump on your wrist on the knife hand side and it extends down like a chi tendon to the finger tip. now, when you do the pakua hand or the hung ga salute you feel the blood fill up along the line to the bulge... why does kung fu do it?