How to Make Someone Die of Laughter, 13th century

Vein Man needs some armpit phlebotomy, stat.
BL Harley 3719, f. 158v (14th c.)

"Beneath the armpits are certain veins called "ticklish" which, if they are cut, cause a man to die of laughter." 

Richardus Salernitanus (13th c.?)

Tired of people not laughing at your jokes? You could just stab them in the armpits...