Several years later Tarnier, who was to become an eminent obstetrician, but was then a student in Paris, chose the diseases of the lying-in period as the subject for his graduating thesis. He was unacquainted with the work either of Holmes or of Semmelweiss, and approached the problem from still another standpoint, drawing attention to the much higher deathrate among women delivered amid unsanitary surroundings. Tarnier also considered that the disease was a form of poisoning, that it was contagious, and that measures should be instituted to protect patients against it. Of these pioneers, by far the greatest credit is due Semmelweiss, who devoted his life to the problem, although his opinions continually met with scepticism and even ridicule. More convincing proof than he could furnish was demanded before his contemporaries would believe that child-bed fever was due to lack of precaution. Fortunately the evidence was soon produced. In 1880, Pasteur obtained bacteria from the organs which had been infected, and was able to grow the bacteria in his laboratory; thus the ultimate cause of the disease became firmly established. With the harmful agents in their hands, Pasteur and his followers were enabled to study their characteristics and to recommend means of destroying them. Much as we must regret that the warnings of Holmes and of Tarnier passed unheeded; lamentable as may be the blindness of the generation of Semmelweiss to the truths revealed by his research, it is not surprising that such radical teaching met with a hostile reception. As we measure time in retrospect from the vantage ground of to-day, the three to four decades required for full acceptance of their revolutionary doctrines seem a brief span. Antiseptic methods would not have prevailed so quickly as they did, had not the same epoch which gave us a Pasteur also given a surgeon with a receptive mind, ready to seize and apply the discoveries of the French genius. This was the great service of Joseph Lister. Impressed with Pasteur's studies on fermentation, Lister saw an analogy between this process and the putrefaction of wounds, a condition which he was eager to prevent. He had reason to believe that carbolic acid would check decomposition, and he employed a weak solution of it in the treatment of wounds; later he devised a "carbolic spray," by means of which when his operations were performed the atmosphere round about might be sterilized.