ON THE MODE OF COMMUNICATION OF CHOLERA. BY JOHN SNOW, M.D., MEMBER OF THE ROYAL COLLEGE OF PHYSICIANS, FELLOW OF THE ROYAL MED. AND CHIR. SOCIETY, FELLOW AND VICE-PRESIDENT OF THE MEDICAL SOCIETY OF LONDON. Second Edition, much Enlarged. LONDON: JOHN CHURCHILL, NEW BURLINGTON STREET. M.DCCC.LV. LONDON: T. RICHARDS, 37 GREAT QUEEN STREET. PREFACE TO THE SECOND EDITION. The first edition of this work, which was published in August 1849, was only a slender pamphlet. I have, since that time, written various papers on the same subject, which have been read at the Medical Societies, and published in the medical journals. The present edition contains the substance of all these articles, together with much new matter, the greater part of which is derived from my own recent inquiries. I take this opportunity of expressing my thanks to the Registrar-General for the facilities afforded me in making these inquiries. I feel every confidence that my present labours will receive the same kind consideration from the Medical Profession which has been accorded to my former endeavours to ascertain the causes of cholera. Sackville Street, Piccadilly, 11 December, 1854. CONTENTS. PAGE Outline of the history of cholera 1 Cases proving its communication from person to person 3 Cholera not communicated by means of effluvia 9 The pathology of cholera indicates the manner in which it is communicated 10 Analysis of the blood and evacuations in cholera 11 and 14 Cholera is propagated by the morbid poison entering the alimentary canal 15 Evidence of this mode of communication in the crowded habitations of the poor 17 —— amongst the mining population 19 Instances of the communication of cholera through the medium of polluted water, in Horsleydown 23 —— at Albion Terrace, Wandsworth Road 25 —— at Ilford and near Bath 32 —— at Newburn on the Tyne 33 —— at Cunnatore 35 —— in the Black Sea Fleet 36