Produced by Stacy Brown, Peter Vachuska, Julia Miller and the Online Distributed Proofreading Team at https://www.pgdp.net OUTLINES OF DAIRY BACTERIOLOGY A CONCISE MANUAL FOR THE USE OF STUDENTS IN DAIRYING BY H. L. RUSSELL Dean of the College of Agriculture University of Wisconsin AND E. G. HASTINGS Professor of Agricultural Bacteriology University of Wisconsin _TENTH EDITION_ MADISON, WISCONSIN H. L. RUSSELL 1914 Copyright 1914 BY H. L. RUSSELL AND E. G. HASTINGS PREFACE TO THE TENTH EDITION. This text was originally the outgrowth of a series of lectures on the subject of dairy bacteriology to practical students in the winter Dairy Course in the University of Wisconsin. The importance of bacteriology in dairy processes has now come to be so widely recognized that no student of dairying regards his training as complete until he has had the fundamental principles of this subject. The aim of this volume is not to furnish an exhaustive treatise of the subject, but an outline and sufficient detail to enable the general student of dairying to obtain as comprehensive an idea of the bacteria and their effects on milk and other dairy products as may be possible without the aid of laboratory practice. When possible the dairy student is urged to secure a laboratory knowledge of these organisms, but lacking this, the student and general reader should secure a general survey of the field of bacteriology in relation to dairying. In this, the tenth edition, the effort has been made to include all of the recent developments of the subject. Especially is this true in regard to the subject of market milk, a phase of dairying that has gained greatly in importance in the last few years. The changes in the methods of handling market milk have been marked. The results of these changes in influencing the quality of milk offered to the consumer are fully discussed. H. L. R. E. G. H. CONTENTS Structure, Growth and Distribution of Bacteria 7 Methods of Studying Bacteria 20 Contamination of Milk 28 Infection of Milk with Pathogenic Bacteria 62 Fermentations of Milk 82 Preservation of Milk 113 Bacteria and Butter Making 136 Bacteria and Cheese Making 161 Bacteria in Market Milk 189 CHAPTER I. STRUCTURE, GROWTH AND DISTRIBUTION. =Relation of bacteriology to dairying.= The arts which have been developed by mankind have been the outgrowth of experience. Man first learned by doing, _how_ to perform these various activities, and a scientific knowledge of the underlying principles which govern these processes was later developed.