The term "encephalitis" has come into general use only since the great epidemic swept the world in 1917-1919. Prior to that time acute encephalitis was not recognized except for those types due to syphilis, trauma or sepsis. Many cases caused by other agents, presumably the filtrable viruses, have now come to light. This volume gives the reports on forty-five patients, all children, showing a wide variety of symptoms and signs pointing to a diffuse lesion in the brain. Epidemic (lethargic) encephalitis is excluded. The group is diffuse. Some cases followed vaccination; others followed chickenpox, measles, scarlet fever, diphtheria and other childhood diseases. Others appeared without preceding disease. The presentation of such a wide variety of material, without more complete classification, only leads to confusion. Although the bibliography is somewhat useful, the book itself cannot be highly recommended.