Gathered in a kind of pen formed by a little fence were three members of the institution: a secretary, whose business it is to keep track of the number of persons to be treated with each particular virus; an assistant, who has prepared the virus for the day's use; twelve small wine glasses of cloudy liquid protected by small paper funnels; and, by a table, the inoculator. The roll was called and a half dozen men entered the room. They were to be inoculated with a virus of the lowest strength, most of them for the first time. They showed a bewildered and comic embarrassment as the attendant directed them to bare the hypogastrium. The embarrassment changed to a momentary look of distress as they felt their arms pinned behind their backs, and the sharp needle injected a syringeful of virus into the delicate flesh. The first class of men and boys passed out, and the women and little children entered. They were succeeded by a second class, and so on until all had been treated. The simplicity of the operation seemed out of proportion to the horror of the disease. I remembered the shrugs I had seen and the doubts I had heard expressed over the treatment. "It is not sure yet." "It does not always work; such-a-one died, you know." "They have not found the microbe either." My faith was shaking. Evidently I must see Doctor Roux. On the second floor of the building I found the office and private laboratory of the under-director of the Pasteur Institute, a man whose researches in connection with Pasteur, whose devotion in the cholera mission in Egypt in 1883, and whose independent investigations on diphtheria, have made him famous in the medical world. The office was small, and it had something of the attraction of a curio shop. There was none of the precision of the man of small affairs here. It was the confusion of the man of big affairs, who cannot endure to have his things meddled with. Over a table where culture tubes, blow-pipes, virus glasses and bottles filled with suspicious-looking fluids were scattered promiscuously around a valuable microscope, hung a gem of a painting--a dashing charge of cavalry. Beside a case of books, and partly concealing a fine portrait of Pasteur, hung the gray-white laboratory blouses of M. Roux. Under an exquisite etching askew in a corner stood a cage of brown-and-white guinea-pigs, martyrs to science, probably. [Illustration: AT THE JUBILEE OF M. PASTEUR. THE PRESIDENT OF THE REPUBLIC WELCOMING M. PASTEUR IN THE AMPHITHEATRE OF THE OLD SORBONNE.] Curiosity was cut short, for a quick step was heard in the outer room, and Doctor Roux entered. A slight figure, bent a little from a life spent over books, tubes and microscopes, but tingling to the finger-tips with nervous energy; a face a little pale, but fresh in color; brown hair and beard, glowing brown eyes, perhaps forty years--such is this eminent associate of Pasteur. As he runs over the pile of letters cut and awaiting him, he talks.