Koch was twenty-one years the junior of Pasteur; but his enthusiasm and genius now bore him rapidly to a fame as great as that of his predecessor. His first remarkable achievement was a demonstration of the cause and cure of splenic fever in cattle. He showed, just as Pasteur had done in similar cases, that the plague in question was due to the specific poison of a bacterium, and that the disease might be cured by inoculation against it. This he proceeded to do, and the demonstration and good work brought him to the attention of the old Emperor. Dr. Koch was made a member of the Imperial Board of Health in Berlin.
A greater discovery was already at the door. Dr. Koch began a careful investigation into the nature of consumption. His discovery of the germ of splenic fever, and that of chicken cholera, as well as the general results in this direction in other laboratories of Europe, led him to the conjecture that consumption also is a zymotic or bacterial disease. His inquiry into this subject began in 1879, and extended to March of 1882. On that day, in a paper before the Physiological Society of Berlin, he announced the discovery of the _tubercle bacillus_. He was able to demonstrate the existence of the germ of consumption, and to describe its methods of life, as well as the character of his ravages.
Here then at last was laid bare the true origin of the most fatal disease which has ever afflicted mankind. He who has not informed himself with respect to the almost universal prevalence of consumption among the nations of the earth, or taken note of the mortality from that dreaded enemy, by which nearly one-sixth of the human race sooner or later perishes, will not have realized the awful character of this enemy. To attack such a foe, to force him into a corner, even as Siegfried did the Grendel in his cavern, was an achievement of which the greatest of mankind might well be proud.
The discovery of the bacillus of consumption by no means assured the cure of the disease; but it foretokened the time when a cure would be found. This prophecy, though it has not yet been clearly fulfilled, is, in the closing years of the century, in process of fulfillment. The enemy does not readily yield; but such has been the gain in the contest that already within the last twenty years the mortality from consumption of the lungs has fallen off more than forty per cent! Much of this gain has been made by the reviving confidence of human beings that sooner or later tuberculosis would be destroyed. Hygiene has done its part; and other circumstances have conduced to the same result. Though neither Dr. Koch nor any other man living has been able as yet positively to meet and vanquish consumption in open battle, yet the goblin has in a measure been robbed of his terrors. He is no longer boastful and victorious over the human race.