"Y-y-y-es—I guess so," he answered, rather vacantly; "I don't know. I don't know anything about it. I never saw such doings. What is it all for? What does it mean?"
"Oh, this is nothing; it's all in a lifetime. Still, I admit it might ha' been serious for us—and you, too—if we hadn't got help."
"But who are they, and what? They all seem of a family, and are killing each other."
"Immortal shade of Darwin!" exclaimed the other sentry, who had not spoken before. "Where were you brought up? Don't you know that variations from type are the deadliest enemies of the parent stock? These two brown breeds are the hundredth or two-hundredth cousins of the black kind. When they've killed off their common relative, and get to competing for grub, they'll exterminate each other, and we'll be rid of 'em all. Law of nature. Understand?"
"Oh, y-yes, I understand, of course; but what did the black kind attack me for? And what do they want, anyway?"
"To follow out their destiny, I s'pose. They're the kind of folks who have missions. Reformers, we call 'em—who want to enforce their peculiar ideas and habits on other people. Sometimes we call them expansionists—fond of colonizing territory that doesn't belong to them. They wanted to get through the cells to the lymph-passages, thence on to the brain and spinal marrow. Know what that means? Hydrophobia."
"What's that?"
"Oh, say, now! You're too easy."
"Come, come," said the other, good-naturedly; "don't guy him. He never had our advantages. You see, neighbor, we get these points from the subjective brain, which knows all things and gives us our instructions. We're the white corpuscles,—phagocytes, the scientists call us,—and our work is to police the blood-vessels, and kill off invaders that make trouble. Those red-and-gray chumps can't take care of themselves, and we must protect 'em. Understand? But this invasion was too much for us, and we had to have help from outside. You must have come in with the first crowd—think I saw you—in at the bite. Second crowd came in through an inoculation tube, and just in time to pull you through."
"I don't know," answered our bewildered friend. "In at the bite? What bite? I was swimming round comfortable-like, and there was a big noise, and then I was alongside of a big white wall, and then——"