“Did you get the message I sent you about Letter Number Seven?” she asked.

“Hello, Milly,” greeted the presiding genius, pleasantly.  “Just what was that about Number Seven?”

“It isn’t getting results.”

“No?  Let’s see it.”  Dr. Surtaine was as interested in this as he had been casual about the drug alteration.

“I don’t think it’s personal enough,” pursued the girl, handing him a sheet of imitation typewriter print.

“Oh, you don’t,” said her employer, amused.  “Maybe you could better it.”

“I have,” said the girl calmly.  “You always tell us to make suggestions.  Mine are on the back of the paper.”

“Good for you!  Hal, here’s the prettiest girl in the shop, and about the smartest.  Milly, this is my boy.”

The girl looked up at Hal with a smile and brightened color.  He was suddenly interested and appreciative to see to what a vivid prettiness her face was lighted by the raised glance of her swift, gray-green eyes.

“Are you coming into the business, Mr. Surtaine?” she asked composedly, and with almost as proprietary an air as if she had said “our business.”

“I don’t know.  Is it the sort of business you would advise a rather lazy person to embark in, Miss—­”

“Neal,” she supplied; adding, with an illustrative glance around, upon her busy roomful, all sorting and marking correspondence, “You see, I only give advice by letter.”

She turned away to answer one of the subordinates, and, at the same time, Dr. Surtaine was called aside by a man with a shipping-bill.  Looking down the line of workers, Hal saw that each one was simply opening, reading, and marking with a single stroke, the letters from a distributing groove.  To her questioner Milly Neal was saying, briskly: 

“That’s Three and Seven.  Can’t you see, she says she has spots before her eyes.  That’s stomach.  And the lameness in the side is kidneys.  Mark it ‘Three pass to Seven.’  There’s a combination form for that.”

“What branch of the work is this?” asked Hal, as she lifted her eyes to his again.

“Symptom correspondence.  This is the sorting-room.”

“Please explain.  I’m a perfect greenhorn, you know.”

“You’ve seen the ads. of course.  Nobody could help seeing them.  They all say, ’Write to Professor Certain’—­the trade name, you know.  It’s the regular stock line, but it does bring in the queries.  Here’s the afternoon mail, now.”

Hundreds upon hundreds of letters came tumbling from a bag upon the receiving-table.  All were addressed to “Prof.” or “Dr.”  Certain.

“How can my father hope to answer all those?” cried Hal.

The girl surveyed him with a quaint and delicious derision.  “He?  You don’t suppose he ever sees them!  What are we here for?”

“You do the answering?”