What does "I sing the body electric" mean anyway?

This contains one of my favorite passages in all literature:

Don’t you hear them pass? hover? dance their language? telling where all the sweet gums are, the syrups that make bears frolic and lumber in bulked ecstasies, that make boys squirm with unpronounced juices, that make girls leap out of beds to catch from the corners of their eyes their dolphin selves naked aflash on the warm air poised forever in one eternal glass wave.