"Grondrig of Human Delayed Heredity and Racial Hygiene (2/2) Human Selection and Racial Hygiene" - a book authored by Fritz Lenz, is the final part of the study of genetics, heredity and influence on human health. In this book, the author examines the issue of rational selection of individuals to maintain strong genetic characteristics, and also seeks to highlight important aspects of racial hygiene. Using scientific evidence and reasoning, Lenz analyzes the influence of heredity on the development of human society and suggests ways to increase the level of health and life opportunities of people through effective selection. The book opens a new perspective on the relationship between genetics and hygiene in the era of the growth of medical science and biology."