BACTERIA IN DAILY LIFE BY MRS. PERCY FRANKLAND FELLOW OF THE ROYAL MICROSCOPICAL SOCIETY; HONORARY MEMBER OF BEDFORD COLLEGE, UNIVERSITY OF LONDON; JOINT AUTHOR OF "MICRO-ORGANISMS IN WATER," "THE LIFE OF PASTEUR," ETC. "Spirits, when they please, Can either sex assume, or both; so soft And uncompounded is their essence pure, Not tied or manacled with joint or limb, Nor founded on the brittle strength of bones, Like cumbrous flesh; but, in what shape they choose, Dilated or condensed, bright or obscure, Can execute their aery purposes, And works of love or enmity fulfil." MILTON. LONGMANS, GREEN, AND CO. 39 PATERNOSTER ROW, LONDON NEW YORK AND BOMBAY 1903 _All rights reserved_ Transcriber's Note: Minor typographical errors have been corrected without note. Irregularities and inconsistencies in the text have been retained as printed. Words printed in italics are noted with underscores; _italics_. The cover of this ebook was created by the transcriber and is hereby placed in the public domain. PREFACE The title of this little volume sufficiently explains its contents; it only remains to add that much of the text has already appeared from time to time in the form of popular articles in various magazines. It has, however, been carefully revised and considerably added to in parts where later researches have thrown further light upon the subjects dealt with. G. C. FRANKLAND NORTHFIELD, WORCESTERSHIRE, _November, 1902_ CONTENTS PAGE BACTERIOLOGY IN THE VICTORIAN ERA 1 WHAT WE BREATHE 34 SUNSHINE AND LIFE 65 BACTERIOLOGY AND WATER 93 MILK DANGERS AND REMEDIES 118 BACTERIA AND ICE 149 SOME POISONS AND THEIR PREVENTION 168 BACTERIA IN DAILY LIFE BACTERIOLOGY IN THE VICTORIAN ERA A little more than sixty years ago the scientific world received with almost incredulous astonishment the announcement that "beer yeast consists of small spherules which have the property of multiplying, and are therefore a living and not a dead chemical substance, that they further _appear_ to belong to the vegetable kingdom, and to be in some manner intimately connected with the process of fermentation." When Cagniard Latour communicated the above observations on yeast to the Paris Academy of Sciences on June 12, 1837, the whole scientific world was taken by storm, so great was the novelty, boldness, and originality of the conception that these insignificant particles, hitherto reckoned as of little or no account, should be endowed with functions of such responsibility and importance as suggested by Latour.