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There is so much of interest in this book that ‘intelligent laymen’ should not be too dispirited at the sprinkling of pharmacological and neurophysiological terms and research
findings. There are handy, not-too-technical summaries at the end of each chapter, and the author's general grasp and teaching ability ensure that his arguments are well put over and tactfully re-stated in various ways. An adequate approach to research on sleep would, I suppose, inevitably have to try to combine the approaches of physiology, pharmacology, dynamic psychology and academic psychology. To achieve this and intelligibility too is in itself a worthwhile operation.
In this book Hartmann discusses why we need sleep in the sense of what sleep does for us. As a consequence of the well-publicized results from the various sleep laboratories, we are all familiar with the two types of sleep, the ‘S’ sleep, occurring mainly in the first few hours of sleep, and the ‘D’ sleep, with its dreaming and rapid eye movements, occurring in several spells throughout the whole period of sleep. Dr Hartmann suggests that the ‘S’ sleep is necessary for the physical restoration of mind and body, involving the re-synthesis of complex molecules. Some of these are necessary for the successful carrying-out of the processes involved in ‘D’ sleep, which bring about recovery from mental strain. In this phase connexions are made between recently learned patterns and already-established ones. Hartmann notes that, although sleep research has come a long way, the two functions he is proposing merely add precision to Shakespeare's formula. Thus let ‘S’—‘chief nourisher at life's feast’—prepare for ‘D’, ‘that knits up the ravelled sleeve of care’.
The chapter on the differences between short sleepers (five hours per night) and long sleepers (nine hours) which were found in his subjects is one of the most interesting and telling in the book. The long sleepers are long sleepers because they need more D-sleep, whereas both g