Dr. Morgan's assistant was a young man whom nature had supplied with a prematurely bald head, a flourishing beard, and a way of appearing ten years older than he really was. To these gifts, priceless to a young medical man, might be added boundless ambition and considerable common sense. The yellow envelope which contained the few lines meaning life or death to little Hiram Joash Baker was delivered at Dr. Morgan's Back Bay office at ten minutes past ten. Dr. Payson--that was the assistant's name--was out, but Jackson, the colored butler, took the telegram into his employer's office, laid it on the desk among the papers, and returned to the hall to finish his nap in the armchair. When Dr. Payson came in, at 11:30, the sleepy Jackson forgot to mention the dispatch. The next morning as Jackson was cleaning the professional boots in the kitchen and chatting with the cook, the thought of the yellow envelope came back to his brain. He went up the stairs with such precipitation that the cook screamed, thinking he had a fit. “Doctah! Doctah!” he exclaimed, opening the door of the assistant's chamber, “did you git dat telegraft I lef' on your desk las' night?” “What telegraph?” asked the assistant sleepily. By way of answer Jackson hurried out and returned with the yellow envelope. The assistant opened it and read as follows: Send 1,500 units Diphtheritic Serum to me by morning train. Don't fail. Utmost importance. J. S. MORGAN. Dr. Payson sprang out of bed, and running to the table took up the Railway Guide, turned to the pages devoted to the O. C. and C. C. Railroad and ran his finger down the printed tables. The morning train for Cape Cod left at 7:10. It was 6:45 at that moment. As has been said, the assistant had considerable common sense. He proved this by wasting no time in telling the forgetful Jackson what he thought of him. He sent the latter after a cab and proceeded to dress in double-quick time. Ten minutes later he was on his way to the station with the little wooden case containing the precious antitoxin, wrapped and addressed, in his pocket. It was seven by the Arlington Street Church clock as the cab rattled down Boylston Street. A tangle of a trolley car and a market wagon delayed it momentarily at Harrison Avenue and Essex Street. Dr. Payson, leaning out as the carriage swung into Dewey Square, saw by the big clock on the Union Station that it was 7:13. He had lost the train. Now, the assistant had been assistant long enough to know that excuses--in the ordinary sense of the word--did not pass current with Dr. Morgan. That gentleman had telegraphed for antitoxin, and said it was important that he should have it; therefore, antitoxin must be sent in spite of time-tables and forgetful butlers. Dr. Payson went into the waiting room and sat down to think. After a moment's deliberation he went over to the ticket office and asked: “What is the first stop of the Cape Cod express?” “Brockboro,” answered the ticket seller.