James N. Pinkerton published Sleep and its Phenomena in 1839. The essay is a revision of a lecture first given to the medical faculty of the University of Edinburgh. In this work Pinkerton introduces his theory of types of sleep, analysing sleep in terms of its completeness. He follows with discussions of dreaming, sleepwalking, spectral illusions, sleep-time apparitions, hibernation and the sleep of plants, analysing each sleep-time activity in terms of sleep type. This work was one of the first to link the activities of the facial muscles and the nervous system during sleep with dreamed movements, thoughts and emotions. It was a pioneering work of nineteenth-century medical research into sleep and helped to establish Pinkerton's reputation. He is still well known today as one of the first to find a correspondence between sleep-actions and dreamed thoughts. It is an important work of Victorian medical research.