EVIDENCES

OF THE

COMMUNICABILITY OF CONSUMPTION.

CHAPTER I.

INTRODUCTORY.

THE belief that consumption is a communicable disease, has long been popularly accepted in many parts of southern Europe, and that popular belief has received the support of the majority of medical men in those countries. Amongst all civilised peoples, this view concerning consumption has, at all events in the last half-century, had its advocates in the medical profession. It was not, however, until 1882 that the belief in the communicability of this disease was established upon a firm foundation. In that year, Dr. Robert Koch demonstrated by observed facts, and by the results of his own experiments, that consumption, as well as every other form of tubercular disease, is caused by a living organism, now known by the name of Koch's bacillus of tubercle. As is usual when new and important truths are first brought into notice, this new teaching received a large amount of adverse criticism, and was met with strong opposition. Scepticism is a valuable help to

A

the progress of truth. That is partly why all reasonable disbelief should receive respectful consideration from those who wish to see scientific truth spreading, not only quickly, but also upon soil properly prepared for its reception, and for its nourishment. To that good end, reasonable doubting of new beliefs works well. A thoughtful and honest critic with a bias towards scepticism, is one of the best helpers of him who first shows the world a scientific discovery. The time inevitably comes when, slowly most likely, but not the less surely, students of the subject are almost as much struck by the breakdown of the attack upon it, as by the steadily increasing weight of evidence which, from various quarters, is brought up in support of the new discovery. Through all these phases Koch's work on tuberculosis has passed. To-day it is no exaggeration to say that this new teaching is regarded, by the great majority of those who are entitled to speak with authority on such matters, as a fact of the first importance in medical science. It surely is right and just, that when a considerable majority of such men express clearly their belief in any new teaching which falls within their ken, then something more than a bare denial of its truth is required of those who decline to believe its doctrines. When, moreover, the teaching in question is based upon evidence founded on experiment, those who doubt or deny its truth are, after a time, if they would maintain their position as just critics, bound either to show error in the experiments themselves, or in the reasoning based upon them. Koch's work concerning tuberculosis hinges upon experiment. No important step in that work is taken which is not

based upon experiment. On the other hand, the objections hitherto advanced against it have no foundation in evidence based upon experiments, which have received recognition from competent authorities. Probably no research of its kind ever had, in a comparatively short time, so much corroboration from work, more or less reliable, done in all quarters of the world. That corroborative work has, to a great extent, been accepted as correct by a very large majority of men whose opinions, on such subjects, are entitled to our best consideration. No doubt, the bulk of the medical profession to-day believe that tubercular disease is caused by a living organism, and that that organism is Koch's bacillus of tubercle. There is not, however, wanting proof of the fact, that there are still those who do not believe either of those propositions. Also, there is prevalent, in certain quarters, a feeling that it can still be truly said of Koch's work on tuberculosis, that it is not yet proved to be correct. Again, there are others who believe it, but who, in their acts and words, do not seem to attach to it any considerable importance. These men appear to regard the work rather as a scientific curiosity, than as a matter full of much practical importance in relation to the question of why from one-fifth to one-seventh of the world's known death-rate is due to tubercular disease.

It may be well to give here an example of those expressions of opinion which, to say the least of them, though not plainly avowing disbelief in Koch's teaching concerning tuberculosis, certainly do not tend to encourage its acceptance. In the Harveian Oration of 1889, Dr. James E. Pollock