“Facts have been found at every step of science which were valueless at their discovery, but which, little by little, fell into line and led to applications of the highest importance--the observation of the tarnishing of silver, the twitching of the frog’s leg, were the origin of photography and telegraphy; the abstract problem of spontaneous generation gave rise to the antiseptics of surgery. . . . In medicine, as in every other practical art, progress depends upon knowledge, and knowledge must be pursued for its own sake without continually looking about for its practical applications. Harvey’s great discovery of the circulation of the blood was a strictly physiological discovery, and had little influence upon the healing art until the invention of auscultation. So, also, Dubois Reymond’s investigation of the electrical properties of muscle and nerve was purely scientific, but we use the results thus obtained every day in the diagnosis of disease, in its successful treatment, and in the scarcely less important demonstration of the falsehoods by which the name of electricity is used for purposes of gain. The experiments on blood pressure, begun by Hales, and carried to a successful issue in our own time by Ludwig, have already led to knowledge which we use every day by the bedside, and which only needs the discovery of a better method of measuring blood pressure during life to become one of our foremost and most practical aids in treatment. Again, we can most of us remember using very imperfect physiological knowledge to fix, more or less successfully, the locality of an organic lesion of the brain. I also remember such attempts being described as a mere scientific game, which could only be won after the player was beaten, since when the accuracy of diagnosis was established, its object was already lost; but who would say this now, when purely physiological research and purely diagnostic success have led to one of the most brilliant achievements of practical medicine, the operative treatment of organic diseases of the brain?” The prevention of disease, as important as its cure, owes an incalculable debt to Louis Pasteur. De Varigny says in “Experimental Evolution”:-- “Pasteur, about 1850, spent a long time in seemingly very speculative and very idle studies of dissymmetry and symmetry in various crystals, especially those of tartaric acid; the practical value of such investigations seemed to be naught, and at all events it had no interest save for the elucidation of some points in crystallography. But this investigation led logically to the study of fermentation, and the final outcome of Pasteur’s work has been--leaving out the stepping stones--the discovery of the real cause of a large number of diseases, the cure of one of them, and the expectation, based on facts, that all these diseases can be defeated by appropriate methods.”