Heredity in Health and Mental Disorder. Principles of Psychiatric Genetics in the Light of Comparative Twin Studies.: By Franz J. Kallmann, M.D. New York: W. W. Norton and Co., Inc., 1953. 315 pp.

In this book the author brings together the results of many years of intensive research into various aspects of human genetics, in particular into the question of inheritance of a predisposition to psychosis. The first part, Heredity in Relation to Mental Health, introduces the reader to the basic elements and current developments in the field of genetics so that he may be sufficiently conversant with the subject to understand the author's later description of his studies. Kallmann has used what he describes as the twin-family method, since this provides 'six categories of genotypically dissimilar sibship groups which can be compared under similar conditions of culture and home milieu'. The six categories are monozygotic (one-egg) twins, dizygotic (two-egg) twins of the same sex, two-egg twins of opposite sex, full sibs, half sibs, and step sibs.

From his studies of more than two thousand twin pairs in the age group over sixty years, the author describes a number of striking cases to prove that similar environments do not result in similar variations in health and adjustment in genetically unlike twins, or dissimilar environments in corresponding dissimilarities in genetically like twins. There is no doubt that he presents sufficient evidence to warrant this conclusion, although one may question his evaluation in individual cases. One might take exception, for example, to his arbitrary assumption, in the discussion of a particular case, that the years between eighteen and sixty-five in 'different' environments would unquestionably be expected to have more influence on personality than the first eighteen. From this premise he deduces that the striking similarities of the now eighty-five-year-old identical twin sisters must be the result of heredity and not environment.

Bringing together evidence from many other workers in the field, Kallmann concludes in this first section of his book that 'human