AGf~ICULTURAL RESEARCH, PUSA.

PREYA_CE
IN prcparing thi:,; fourth cdition, we have again taken
the opportunity of completely revising thc book. The
continued development of the subject in recent years
has neccssitated many additions to the text and the
introduction of modificd methods. In particular, a
new technique for the storage and distribution of
culture medium, involving the substitution of screwcapped
bottles for stoppered test-tubes, has been
described in Chapter IV. An end cavour has been
made to keep the book within a given compass, though
the text has cxpanded with each edition and the
scope has extended considerably beyond what was
conternplated when the first edition was written. In
this edition we have divided the subject-matter into
three parts; the first is of introductory nature and
deals briefly and in a general way with the biology
of micro-organisms and with immunity in relation
to practical bacteriology; the second is devoted to
bacteriological and serological technique; while in
the third part the pathogenic and commensal microorganisms
are described, along with the methods of
bacteriological diagnosis of the various infections.
Part III. includes also a chapter on the viruses, and
this has been considerably extended in the present
edition. We hope that this subdivision may assist
the undergraduate student in using the book: thus,
Pmt n. constitutes the more highly technical section
of the subject and the junior student need only refer
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