familiar with the functions of bacteria in daily life. Through
these agencies the popular misconception of the nature of micro-
organisms and their relations to man is being gradually displaced
by a general appreciation of their manifold services. It is not
unreasonable to hope that the many thousands of copies of this
little manual which have been circulated and read have contributed
materially to that end. If its popularity is a safe criterion, the
book has amply fulfilled its purpose of placing before the general
reader in a simple and direct style the main facts of
bacteriology. Beginning with a discussion of the nature of
bacteria, it shows their position in the scale of plant and animal
life. The middle chapters describe the functions of bacteria in
the arts, in the dairy, and in agriculture. The final chapters
discuss the relation of bacteria to disease and the methods by
which the new and growing science of preventive medicine combats
and counteracts their dangerous powers.

JULY, 1915.





CONTENTS.


I.--BACTERIA AS PLANTS

Historical.--Form of bacteria.--Multiplication of bacteria.--Spore
formation.--Motion.--Internal structure.--Animals or plants?--