The Long-Life Bacillus: A Guide to the Preparation and Acidification of Milk for Food Purposes, Together with a Historical Sketch of the Use of Fermented Milk Products from the Earliest Times to the Present Day and Their Remarkable Prolonging Effects, was written by Douglas and Loudon M. This book is a practical guide to the preparation and acidification of milk for food, and contains an interesting survey of the use of fermented milk products in various historical periods up to the present day. The authors investigate the wonderful properties of fermented dairy products and their impact on human health and life expectancy. This book will be a useful source of information for anyone interested in a healthy lifestyle and diet.