Excerpt from The Sources and Modes of Infection We need to measure more carefully the relative importance of different sources of disease and different modes of infec tion. It is not so important to know that typhoid bacilli live in water for weeks, as it is to know that 99 per cent die in one week. It is not enough to discover that diphtheria bacilli can be recovered from articles in the sick-room; we must learn how often they are found and how often disease is traced to such a source. We have for years been much alarmed because tubercle bacilli are found in milk, but since a serious effort has been made to measure the actual danger, the alarm has greatly diminished. Doubtless the house fly has been the cause of typhoid fever, but in what percentage of cases we are profoundly ignorant. Healthy carriers of diphtheria have certainly transmitted the disease to others, and we should earnestly try to determine the amount of diphtheria caused in this way. The attempt is made in the following pages to estimate roughly, with the very imperfect material now available, the relative importance of different factors in the extension of infectious diseases. The conclu sions must to a large extent be merely tentative, and as indicating lines for further study. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.