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

EIGHTH EDITION
Thoroughly Revised

MADISON, WISCONSIN
H. L. RUSSELL
1907

Copyrighted 1905
BY
H. L. RUSSELL


STATE JOURNAL PRINTING COMPANY,
Printers And Stereotypers,
Madison, Wis.

Transcriber's note: Minor typos have been corrected.

PREFACE.

Knowledge in dairying, like all other technical industries, has grown mainly out of experience. Many facts have been learned by observation, but the why of each is frequently shrouded in mystery.

Modern dairying is attempting to build its more accurate knowledge upon a broader and surer foundation, and in doing this is seeking to ascertain the cause of well-established processes. In this, bacteriology is playing an important rôle. Indeed, it may be safely predicted that future progress in dairying will, to a large extent, depend upon bacteriological research. As Fleischmann, the eminent German dairy scientist, says: "The gradual abolition of uncertainty surrounding dairy manufacture is the present important duty which lies before us, and its solution can only be effected by bacteriology."

It is therefore natural that the subject of Dairy Bacteriology has come to occupy an important place in the curriculum of almost every Dairy School. An exposition of its principles is now recognized as an integral part of dairy science, for modern dairy practice is rapidly adopting the methods that have been developed as the result of bacteriological study. The rapid development of the subject has necessitated a frequent revision of this work, and it is gratifying to the writer that the attempt which has been made to keep these Outlines abreast of bacteriological advance has been appreciated by students of dairying.

While the text is prepared more especially for the practical dairy operator who wishes to understand the principles and reasons underlying his art, numerous references to original investigations have been added to aid the dairy investigator who wishes to work up the subject more thoroughly.

My acknowledgments are due to the following for the loan of illustrations: Wisconsin Agricultural Experiment Station; Creamery Package Mfg. Co., Chicago, Ill.; and A. H. Reid, Philadelphia, Pa.

CONTENTS.

Chapter I. Structure of the bacteria and conditions governing their development and distribution 1

Chapter II. Methods of studying bacteria 13

Chapter III. Contamination of milk 19

Chapter IV. Fermentations in milk and their treatment 62

Chapter V. Relation of disease-bacteria to milk 82

Diseases transmissible from animal to man through diseased milk 84

Diseases transmissible to man through infection of milk after withdrawal 94

Chapter VI. Preservation of milk for commercial purposes 102

Chapter VII. Bacteria and butter making 134

Bacterial defects in butter 156

Chapter VIII. Bacteria in cheese 160

Influence Of bacteria in normal cheese processes 160

Influence of bacteria in abnormal cheese processes 182

CHAPTER I.

STRUCTURE OF THE BACTERIA AND CONDITIONS GOVERNING THEIR DEVELOPMENT AND DISTRIBUTION.

Before one can gain any intelligent conception of the manner in which bacteria affect dairying, it is first necessary to know something of the life history of these organisms in general, how they live, move and react toward their environment.

Nature of Bacteria. Toadstools, smuts, rusts and mildews are known to even the casual observer, because they are of evident size. Their plant-like nature can be more readily understood from their general structure and habits of life. The bacteria, however, are so small, that under ordinary conditions, they only become evident to our unaided senses by the by-products of their activity.

When Leeuwenhoek (pronounced Lave-en-hake) in 1675 first discovered these tiny, rapidly-moving organisms he thought they were animals. Indeed, under a microscope, many of them bear a close resemblance to those minute worms found in vinegar that are known as "vinegar-eels." The idea that they belonged to the animal kingdom continued to hold ground until after the middle of the nineteenth century; but with the improvement in microscopes, a more thorough study of these tiny