“Some men.  Soldiers, for instance.  They’re paid to.”

“Good Heavens!  Is it all a question of pay in your mind?  Wouldn’t you, unless you were paid for it?”

“How can I tell until the occasion arises?”

“Are you afraid?”

“I suppose I might be.”

“Hasn’t the man any blood in his veins?” cried his inquisitor, exasperated.  “Haven’t you ever been angry clear through?”

“Oh, of course; and sorry for it afterward.  One is likely to lose one’s temper any time.  It might easily happen to me and drive me to make a fool of myself, like—­like—­” His voice trailed off into a silence of embarrassment.

“Like Fitzhugh Carroll.  Why not say it?  Well, I much prefer him and his hot-headedness to you and your careful wisdom.”

“Of course,” he acquiesced patiently.  “Any girl would.  It’s the romantic temperament.”

“And yours is the scientific, I suppose.  That doesn’t take into account little things like patriotism and heroism, does it?  Tell me, have you actually ever admired—­really got a thrill out of—­ any deed of heroism?”

“Oh, yes,” he replied tranquilly.  “I’ve done my bit of hero worship in my time.  In fact, I’ve never quite recovered from it.”

“No!  Really?  Do go on.  You’re growing more human every minute.”

“Do you happen to know anything about the Havana campaign?”

“Not much.  It never seemed to me anything to brag of.  Dad says the Spanish-American War grew a crop of newspaper-made heroes, manufactured by reporters who really took more risks and showed more nerve than the men they glorified.”

“Spanish-American War?  That isn’t what I’m talking about.  I’m speaking of Walter Reed and his fellow scientists, who went down there and fought the mosquitoes.”

The girl’s lip curled.

“So that’s your idea of heroism!  Scrubby peckers into the lives of helpless bugs!”

“Have you the faintest idea what you are talking about?”

His voice had abruptly hardened.  There was an edge to it; such an edge as she had faintly heard on the previous night, when Carroll had pressed him too hard.  She was startled.

“Perhaps I haven’t,” she admitted.

“Then it’s time you learned.  Three American doctors went down into that pesthole of a Cuban city to offer their lives for a theory.  Not for a tangible fact like the flag, or for glory and fame as in battle, but for a theory that might or might not be true.  There wasn’t a day or a night that their lives weren’t at stake.  Carroll let himself be bitten by infected mosquitoes on a final test, and grazed death by a hair’s breadth.  Lazear was bitten at his work, and died in the agony of yellow-fever convulsions, a martyr and a hero if ever there was one.  Because of them, Havana is safe and livable now.  We were able to build the Panama Canal because of their work, their—­what did you call it?—­scrubby peeking into the lives of—­”