The writer's experience as a health officer and as a teacher has led him to believe that there is need for a book telling something about milk, how it is produced and how it is transported and delivered to city milk consumers and of the methods of control adopted to insure its purity. The subject is a broad one and in its divisions touches several specialized fields which are the domain of experts so that necessarily the work of these men has been drawn on for material. The attempt has been made to give them due credit by lists of sources at the end of each chapter. To the many dairymen and city milk dealers who have given cordial welcome to their farms and plants, to those who have supplied photographs and to the friends who have helped with advice in the preparation of the manuscript and in revision of the proof the author gives hearty thanks.