Page:The Harveian oration - delivered at the Royal College of Physicians, London, June 24, 1870 (IA b22307643).pdf/50

 or dust and fermentation, since the re- lation of dust to disease has not been revealed anywhere in the inquiry. That the air conveys the material causes of in- fectious diseases from the sick to the healthy, is a notorious fact, which had equal force before these inquiries were instituted, though, owing to the exigencies of social intercourse, it is a fact now more neglected than in times of comparative ignorance.

It is difficult to vindicate exactness in progress without seeming to be at the same time a hinderer of it. The onward and the regulating forces of a machine, though not incompatible, but necessary, require the nicest balance. This reflection suggests itself by the way the spread of infectious diseases has been handled. The theories it has given rise to have been so easily put forward as to thereby create distrust. But the spirit of science is no favourer of nega- tions. "Der Geist der stets verneint" finds no greater friend in medicine than in theo- logy. But it will be admitted that no