The Bacillus of Long Life A Manual of the Preparation and Souring of Milk for Dietary Purposes, Together with an Historical Account of the Use of Fermented Milks, from the Earliest Times to the Present Day, and Their Wonderful Effect in the Prolonging of Human Existence

"The Bacillus of Long Life" by Loudon M. Douglas is a scientifically-minded book examining the historical and health-related aspects of soured milk's preparation and consumption. It explores how fermented milks, like yogurt and kefir, have been used throughout history, particularly in regions known for the longevity of their inhabitants. The book looks at the connection between these milks and their health benefits in order to understand how they promote longer lives. It begins by sharing various historical accounts and practices related to milk consumption and its preparation and considers the cultures that have traditionally valued soured milk as part of their diet, with special attention to the possible link between these habits and longer lifespans.