An electrical signal jumps down a nerve axon. Pop! The signal reaches the end of the axon where tiny packets of chemicals burst open into a minute space between two cells. These chemicals, known as neurotransmitters, cause the next neuron in line to become active and send its own electrical signal, propagating the message forward towards its target. This is the current paradigm of neurotransmission how neurons communicate with one another and it forms the fundamental framework for the entire field of neuroscience. However, this "neuron theory" (as it is known) was not the traditional model held by most scientists through much of history.
Any book about genetics that chooses a William Blake poem as its epigram is one in which many literary and scientific lines will be crossed. Jonathan Weiner's Time, Love, Memorydoes just that, as it delves into the origins of fruit fly genetics.