The third edition of Noguchi's work differs little from the previous one in the account of the technic of the Wassermann test and its modifications. By the use of extracts of pure cultures of the Spirochaeta pallida the author has been able to show that in early cases of syphilis it is not a true specific antibody that gives the positive result to the Wassermann reaction, although such an antibody is found in immunized animals and in some of the late cases of human syphilis. These findings suggest new problems in diagnosis and prognosis of the disease. A chapter is added on the luetin reaction, illustrated by several colored plates. The book thus brings the serodiagnosis of syphilis fully up to date.