ΤΟ

PROFESSOR ROBERT KOCH, M.D.,

TO WHOSE GENIUS AND BRILLIANT WORK

MAN ALREADY OWES A DEBT

HE CAN NEVER PAY,

This Book is Dedicated,

WITH GREAT RESPECT AND ADMIRATION,

BY HIS FORMER PUPIL,

THE AUTHOR.

PREFACE.

LAST winter, at the City of London Hospital for Diseases of the Chest, I gave two lectures entitled "The Question of the Communicability of Consumption." It was not then my intention to publish the lectures, because what there may have been of interest in them was, of necessity, a résumé of the evidence relating to that question, and had already been laid before the medical profession.

Some of those who were among my audience on the occasions referred to, suggested to me that what I then said should be put into book form, for convenience of reference. After much hesitation and delay, I decided to follow this suggestion, and to embody the substance of the lectures in short chapters. It has, therefore, been necessary to alter much of the wording of the original manuscript, and to add to it, here and there.

About a month before the lectures were delivered, I wrote to Prof. Koch, and asked him if he could let me have some references to recent contributions to medical literature, for use in my preparation for

these lectures. I had hoped to receive from him a few words in reply, indicating where what I wanted was to be found. To my surprise, he sent me what now forms the Appendix to this book. Unfortunately, his very kind and valuable assistance was not available for my lectures, for his manuscript reached me after they had been delivered. It seemed to me a pity, that such a useful synopsis of current literature upon so important a subject, should not be used; and, therefore, it is now placed at the service of those who may desire or need its help.

The record of cases given in the Appendix was made, at Prof. Koch's request, by Dr. Frosch, of Berlin, who most kindly gave me permission to publish it in its present form. I cannot sufficiently thank Dr. Frosch for his courtesy and kindness in placing this remarkably accurate piece of work at my disposal.

I heartily thank all those who have so kindly helped me in my attempt to deal, in a few pages, with a very important subject.

HARLEY STREET, W.

October 1890.