CHAPTER V SERVICES RENDERED TO SCIENCE AND HUMANITY BY EXPERIMENTAL PHYSIOLOGY I now come to a favourite theme of anti-vivisectionists, viz., that experimental physiology has produced nothing, and that the differences of opinion among _savants_ are so considerable that this alone proves the impossibility of vivisection ever establishing anything permanent. Here again it is difficult to reply because of the very ignorance of the honourable gentlemen who criticise us. Most certainly there still remain many disputed and disputable points in physiology, and nothing is easier than to find therein striking and abundant contradictions. If we wished to amuse ourselves, we might write five or six big volumes on the subject; but let us leave this tedious and useless labour to the anti-vivisectionists to accomplish to their hearts' content. I prefer to tell them, what they do not wish to know perhaps, that contradiction is the very essence of science. As our demonstrations appeal not to faith but to reason; as we admit free discussion, free investigation from every side; any proposition must have multitudinous and positive proofs in its favour before it can be adopted without hesitation. Even our opinions were never prescribed by faith or violence; we take pleasure in provoking discussion and contradiction. With our adversaries' leave be it said that a dogmatic, irreproachable book, where there was no place for hesitation or doubt, would be the very negation of science. Even the treatises of geometry and mechanics, although non-experimental, rational sciences, sometimes contradict themselves. It has been rightly said that the history of science is the history of human errors--errors which, little by little, draw nearer and nearer to supreme truth without ever attaining it. We must understand this, or we shall be rebelling against the conception of scientific truth. Now, in treatises on physiology, we find a number of well-demonstrated truths, and a still larger number of truths only half demonstrated, and, consequently, contested. Our successors will also certainly find in our books of to-day an enormous number of errors. What conclusion is to be drawn from this fact? Have those who reproach the science of physiology with being only a tissue of contradictions and errors ever opened a book on physiology (for example, the text-book of Schaefer, in two large, compact, closely written volumes of 1000 pages each)? They would there find thousands of positive, incontestable facts on all the questions which concern physiology. Let us take, each in its turn, the great functions of life, and we shall see that they have become known only by experimentation. 1. _The Circulation of the Blood_, suspected by Michel Servet, Realdo Colombo, and Andreas Cesalpin, was really established by Harvey in 1628.