Page:Popular Science Monthly Volume 20.djvu/262

250 four years, and might be even pulverized into dust, without losing its power of infection.

Here I would stop to cite the prophetic words used by Professor Tyndall, when giving an account to a Glasgow audience, in 1876, of Koch's then recent researches: "The very first step toward the extirpation of those contagia is the knowledge of their nature; and the knowledge brought to us by Dr. Koch will render as certain the stamping out of splenic fever as the stoppage of the plague of pébrine by the researches of Pasteur."

It was but fitting that the complete verification of this prediction should be the direct result of the labors of the illustrious man on whose previous work it was based, although others were at work, more or less successfully, in the same direction.

One of the first questions examined by Pasteur was the cause of outbreaks of "charbon" in its most deadly form among flocks of sheep feeding in what appeared to be the healthiest pastures, far removed from any obvious source of infection. Learning by the inquiries he instituted that special localities seemed haunted, at distant intervals, by this plague, he inquired what had been done with the bodies of the animals that had died of it, and learned that it had been customary to bury them deep in the soil, and that such interments had been made, it might have been ten years before, beneath the surface of some of the very pastures in which the fresh outbreaks took place. Notwithstanding that the depth (ten or twelve feet) at which the carcasses had been buried seemed to preclude the idea of the upward traveling of the poison-germs, the divining mind of Pasteur found in earth-worms a probable means of their conveyance, and he soon obtained an experimental verification of his idea, which satisfied even those who were at first disposed to ridicule it. Collecting a number of worms from these pastures, he made an extract of the contents of their alimentary canals, and found that the inoculation of rabbits and Guinea-pigs with this extract gave them the severest form of "charbon," due to the multiplication in their circulating current of the deadly anthrax-bacillus, with which their blood was found after death to be loaded.

Another mode in which the disease-germs of anthrax may be conveyed to herds of cattle widely separated from, each other and from any ostensible source of infection was discovered by the inquiries prosecuted, a few years ago, by Professor Burdon-Sanderson at the Brown Institution, in consequence of a number of simultaneous outbreaks which occurred in different parts of the country. It was found that all the herds affected had been fed with brewers' grains supplied from a common source; and, on examining microscopically a sample of these grains, they were seen to be swarming with the deadly bacillus, which, when it has once found its way among them, grows and multiplies with extraordinary rapidity.