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Obvious typographical errors have been silently corrected. Variations in hyphenation have been standardised but all other spelling and punctuation remains unchanged.
Italics are represented thus _italic_, bold thus =bold= and superscripts thus y^{ en}.
The mathematical and chemical formulae accurately represent the original but have not been error checked.
There are many mathematical equations where variables are presented as italic letters. For the sake of clarity this has not been shown.
UNIVERSITY SCHOLAR IN MEDICINE; DIPLOMATE IN PUBLIC HEALTH, UNIV. LOND.; MEDICAL OFFICER OF HEALTH OF BRIGHTON; MEMBER OF THE COUNCIL AND EXAMINER TO THE SANITARY INSTITUTE; EXAMINER IN STATE MEDICINE TO THE UNIVERSITY OF LONDON; LATE EXAMINER IN PREVENTIVE MEDICINE TO THE UNIVERSITY OF OXFORD, AND PRESIDENT OF THE INCORPORATED SOCIETY OF MEDICAL OFFICERS OF HEALTH.
GEO. GILL & SONS, LD., MINERVA HOUSE, WARWICK LANE.
The writing of a preface is perhaps superfluous for a book which has had a large and steady sale for nearly twenty years, and which has evidently met with the approval of a large constituency. A few words of introduction appear, however, desirable in view of the facts that the present edition has been almost entirely re-written; that a large amount of new matter has been introduced; and that, so far as is known, the comments on each subject represent the most recent and authoritative knowledge upon it.
An attempt has been made to meet the requirements of medical students, as well as of science students and general readers, for whom former editions were chiefly intended. A large class of medical students and practitioners do not require the detailed statement of the subject contained in the larger text-books. For them, and, it is hoped, also for a large number of candidates for diplomas in public health and in sanitary science, the present edition will prove to be useful. At the same time, the subject has been treated as non-technically as is consistent with accuracy, in order to retain its suitability for non-medical readers. A large number of new illustrations have been introduced.