processes of generation, wonder with him, as he exclaims, "How long a time is conception to be carried out to parturi- tion with what labour and tenderness is an infant reared but by what a nothing is it destroyed! It takes an Such age to establish cities, an hour to destroy them." 16 thoughts may lead us to ask ourselves-in face of the recent calamities in Marseilles, Naples, and Toulon-do these visitations give sanction to the law of the "survival of the strongest," which was the idea of the generalization of Harvey, or "survival of the fittest," which was that of Darwin? Man dies, nations become extinct, but the Microbe lives on. His earnest cultivators provide him with change of scene, of temperature, of food, and all possible surrounding conditions; and we may almost fancy that we hear the well-tended, and well-cultivated tyrant siuging, to some ghastly accompaniment,-
"Men may come, and men may go; But I go on for ever."
iv. It is difficult to refrain from giving yet another illustra- tion of the mode and degree to which Harvey had forestalled or prepared the way for one of the greatest discoveries since his own time-viz., that of the "reflex action" of the spinal cord. In a letter to Horst, written in 1654-5, he says, looking forward to the work of those who were to follow him, and speaking of himself as "not only far stricken in years, but afflicted with more and more in- different health. . . . I do not doubt but that many things still lie hidden in Democritus's well that are destined to be drawn up into the light by the indefatigable diligence of coming ages."" Following up this thought we find him saying, in his Exercises on Generation, after dis- tinguishing between the action of the organs of sense, 18 On Generation, p. 322. 17 Letters, to Horst and others, p. 613.
