"What improvements in medical practice may be directly attributed to physiological research is a question which can be properly discussed only by those physiologists and medical practitioners who have studied the history of their subjects; but, as far as I can learn, the benefits are already great. However this may be, no one, unless he is grossly ignorant of what science has done for mankind, can entertain any doubt of the incalculable benefits which will hereafter be derived from physiology, not only by man, but by the lower animals. Look, for instance, at Pasteur's results of modifying the germs of the most malignant diseases, from which, as it so happens, animals will, in the first place, receive more relief than man. Let it be remembered how many lives, and what a fearful amount of suffering have been saved by the knowledge gained of parasitic worms through the experiments of Virchow and others on living animals. In the future every one will be astonished at the ingratitude shown, at least in England, to these benefactors of mankind. As for myself, permit me to assure you that I honour, and shall always honour, every one who advances the noble science of physiology. "Dear sir, yours faithfully, "CHARLES DARWIN." As an experimenter Darwin was by no means overconfident either in his methods or his power of obtaining results. He simply took the best means open to him, or that he could devise, applied them in the best way known to him, and calmly studied the result. "As far as my experience goes," he wrote, in reference to experimental work, "what one expects rarely happens." On another occasion, after working like a slave at a certain investigation, "with very poor success;" he remarks, "as usual, almost everything goes differently to what I had anticipated." How few investigators have the magnanimity which appears in this confession. But more than this, it is an indication of the rare patience with which he stuck at a subject till he knew all he could read or discover or develop in connection with it. It was "dogged" that did it; "awfully hard work" sometimes. In reference to an attempt of his to define intelligence, which he regarded as unsatisfactory, after remarking that he tried to observe what passed in his own mind when he did the work of a worm, he writes: "If I come across a professed metaphysician, I will ask him to give me a more technical definition with a few big words, about the abstract, the concrete, the absolute, and the infinite. But sincerely, I should be grateful for any suggestions; for it will hardly do to assume that every fool knows what 'intelligent' means."