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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:

For Text: A word surrounded by a cedilla such as ~this~ signifies that
the word is bolded in the text. A word surrounded by underscores like
_this_ signifies the word is italics in the text. For numbers and
equations, underscores before bracketed numbers in equations denote a
subscript.

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 role. 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.

        H. L. Russell.
           University of Wisconsin.




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
structures was made possible, and their vegetable nature demonstrated.
The bacteria as a class are separated from the fungi mainly by their
method of growth; from the lower algae by the absence of chlorophyll,
the green coloring matter of vegetable organisms.

~Structure of bacteria.~ So far as structure is concerned the bacteria
stand on the lowest plane of vegetable life. The single individual is
composed of