Dr Walter begins with a history of the evolution of the brain, and describes to us something of the meaning of "that enchanted loom where millions of flashing shuttles weave a dissolving pattern."
He then tells the story of the invention and perfection of the EEG machine and its clinical use for the diagnosis of brain afflictions. He analyzes, with vivid examples, the rhythmic patterns of personality revealed in different "brain prints," and discusses what light these new electronic processes can throw on memory, vision, fatigue, sleep, hypnotism, genius, lunacy, sex disturbances, crime, and other problems of everyday interest.
He includes descriptions, with wiring diagrams, of the various electrical toys (including the speculatrix or mechanical turtle) which he has himself invented to demonstrate his theories. With an extraordinary gift for language, a minimum of speculation and a maximum of demonstrated fact, Dr Walter has written a truly exciting book, a landmark in the advance of human knowledge.

(From Goodreads)