your ancestors, the monkeys, learned to walk on two legs as you have learned to ride a bicycle, and that… this very old function has well organized centres, but it is none the less a function, that is to say, a complete system of sensations and images.
Janet uses bicycle-riding as the exemplary case for his theory of functional psychological systems, arguing that acquired motor skills form neurological centres that can be dissociated in hysteria just as older phylogenetic functions can be lost.
, The Major Symptoms of Hysteria, 1907thesis