A drop of old tuberculin, which is an extract of tubercle bacilli, is put on the skin and then a small superficial scarification is made by turning, with some pressure, a vaccination lancet on the surface of the skin. The next day only those individuals show an inflammatory reaction at the point of vaccination who have already been infected with tuberculosis, whereas the healthy individuals show no reaction at all. Every time we find a positive reaction, we can say with certainty that the child is tuberculous.

A magician of old waved a wand that he might banish disease, a physician to-day peers through a microscope to detect the bacillus of that disease and plan its defeat. The belief in miracles was premature, that is all; it was based on dreams now coming true.

Facts may belong to the past history of mankind, to the social statistics of our great cities, to the atmosphere of the most distant stars, to the digestive organs of a worm, or to the life of a scarcely visible bacillus. It is not the facts themselves which form science, but the method in which they are dealt with.

From my numerous observations, I conclude that these tubercle bacilli occur in all tuberculous disorders, and that they are distinguishable from all other microorganisms.

I can think of a few microorganisms, possibly the tubercle bacillus, the syphilis spirochete, the malarial parasite, and a few others, that have a selective advantage in their ability to infect human beings, but there is nothing to be gained, in an evolutionary sense, by the capacity to cause illness or death. Pathogenicity may be something of a disadvantage for most microbes…

In the first papers concerning the aetiology of tuberculosis I have already indicated the dangers arising from the spread of the bacilli-containing excretions of consumptives, and have urged moreover that prophylactic measures should be taken against the contagious disease. But my words have been unheeded. It was still too early, and because of this they still could not meet with full understanding. It shared the fate of so many similar cases in medicine, where a long time has also been necessary before old prejudices were overcome and the new facts were acknowledged to be correct by the physicians.

It is safe to say that the little pamphlet which was left to find its way through the slow mails to the English scientist outweighed in importance and interest for the human race all the press dispatches which have been flashed under the channel since the delivery of the address—March 24. The rapid growth of the Continental capitals, the movements of princely noodles and fat, vulgar Duchesses, the debates in the Servian Skupschina, and the progress or receding of sundry royal gouts are given to the wings of lightning; a lumbering mail-coach is swift enough for the news of one of the great scientific discoveries of the age. Similarly, the gifted gentlemen who daily sift out for the American public the pith and kernel of the Old World's news; leave Dr. KOCH and his bacilli to chance it in the ocean mails, while they challenge the admiration of every gambler and jockey in this Republic by the fullness and accuracy of their cable reports of horse-races.

Man is a noisome bacillus whom Our Heavenly Father created because he was disappointed in the monkey.

To prove that tuberculosis is caused by the invasion of bacilli, and that it is a parasitic disease primarily caused by the growth and multiplication of bacilli, it is necessary to isolate the bacilli from the body, to grow them in pure culture until they are freed from every disease product of the animal organism, and, by introducing isolated bacilli into animals, to reproduce the same morbid condition that is known to follow from inoculation with spontaneously developed tuberculous material.