In 1843 Oliver Wendell Holmes published the paper on "The Contagiousness of Puerperal Fever," which is now preserved in his volume of "Medical Essays." Physicians were startled to be frankly told the responsibility they assumed if they neglected the truth taught by epidemics of this disease. "The dark obituary calendar" which marked the progress of these epidemics clearly indicated that "the disease is so far contagious as to be frequently carried from patient to patient by physicians and nurses." A violent controversy followed this arraignment, and, consequently, the preventive measures which Holmes so convincingly urged were not adopted as promptly as they should have been. The full justice of his conclusions has since been universally admitted, and medical men now find it difficult to understand how anyone could have taken issue with the sentiment which he expressed. "For my part," Holmes said, "I had rather rescue one mother from being poisoned by her attendant than claim to have saved forty out of fifty patients to whom I had carried the disease." But the most important early observations upon child-bed fever were made in 1847 by a young Hungarian, Semmelweiss, while he was an assistant in the large Lying-in Hospital in Vienna. In thoroughness, power of conviction, and practical value his work was masterful. It is no exaggeration to regard his observations as the rock upon which antiseptic surgery, the glory of the nineteenth century, was built. Semmelweiss had been seeking an explanation of the dreadful scourge, and his mind was ready for the reception of the truth when it was revealed through the death of one of his colleagues. This physician injured his finger accidentally in performing an autopsy upon a patient who had died from child-bed fever. And the condition disclosed by examination of his body after death was identical with that found in cases of child-bed fever. Here then was the clew; the disease was contagious. Semmelweiss was ignorant of Holmes' views; what had happened before his eyes suggested to him that the disease was due to a poison which could be conveyed from one person to another. Moreover, his interest and his power of insight led to further comparison. Clearly, the open wound on the physician's finger had been the portal through which the poison entered; but where was there a similar portal in obstetrical patients? The answer was plain. The birth-canal at the time of delivery is always an open wound. There the poison entered, and child-bed fever was a wound infection!