As in all series of vital actions, each item of the phenomenon in question is so interlinked with the rest, that an explanation of a part can never be considered final, so long as any problem remains unresolved. The latest experimentator, brooding over hitherto neglected details, may always hope to light upon some clue that shall unravel the entire entanglement in a different manner, and reform upon a new basis ideas now grouped in pretended fixity. The excitement caused by this possibility is amply sufficient to stimulate research. And there is no need to discover an immediate practical application for the theory in order to bait the interest of vulgar minds. These would always be incapable of such difficult investigations, while really competent students were supremely indifferent to all lesser advantages attached to the discovery of truth. As for me, I had been so long removed from active life and its necessities (for my professional career had as yet been too facile and commonplace to arouse me to them), that the impractical character of the subject constituted for me an additional charm. I recognized that it belonged, for the present at least, to the region of pure thought, pure science, accessible only to intelligences refined by nature, and enriched by superior culture. In addition, therefore, to the intrinsic interest of the problem, and the solid satisfaction arising from acute intellectual activity, I could, in pursuit of this theme, experience all the subtle pleasure derived from a consciousness of personal superiority--pleasure as attainable in solitude as elsewhere since the superiority was too real and unquestionable to require the confirmatory suffrage of the crowd. I abandoned all other studies, and threw myself impetuously into the current of these newly-received ideas. I ransacked my library, from Herophilus to Haller, from Galen to Helmholtz. England, Germany, Italy, France yielded up their tribute to my excited curiosity. And the theme, shifted, refracted from intellect to intellect, multiplied itself to bewildering complexity.