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devil would you get the rabbits? Where would you get sick spinal cord enough to make one-thousandth enough vaccine?"

Then finally there dawned on Pasteur a simple way out of his trouble: "It's not the dogs we must give our fourteen doses of vaccine," he pondered, "it's the human beings that have been bitten by mad dogs. . . ."

"How easy! . . . After a person has been bitten by a mad dog, it is always weeks before the disease develops in him. . . . The virus has to crawl all the way from the bite to the brain. . . . While that is going on we can shoot in our fourteen doses . . . and protect him!" and hurriedly Pasteur called Roux and Chamberland together, to try it on the dogs first.

They put mad dogs in cages with healthy ones, and the mad dogs bit the normal ones.

Roux injected virulent stuff from rabid rabbits into the brains of other healthy dogs.

Then they gave these beasts, certain to die if they were left alone—they shot the fourteen stronger and stronger doses of vaccine into them. It was an unheard-of triumph! For every one of these creatures lived—threw off perfectly, mysteriously, the attacks of their unseen assassins, and Pasteur—who had had a bitter experience with his anthrax inoculations—asked that all of his experiments be checked by a commission of the best medical men of France, and at the end of these severe experiments the commission announced:

"Once a dog is made immune with the gradually more virulent spinal cords of rabbits dead of rabies, nothing on earth can give him the disease."

From all over the world came letters, urgent telegrams, from physicians, from poor fathers and mothers who were waiting terror-smitten for their children, mangled by mad dogs, to die—frantic messages poured in on Pasteur, begging him to send them his vaccine to use on threatened humans. Even the magnificent Emperor of Brazil condescended to write Pasteur, begging him . . .

And you may guess how Pasteur was worried! This was no