For the Fourth Men, the Great Brains, there was no possible life but the life of intellect; and the life of intellect had become barren. Evidently something more than mere bulk of brain was needed for the solving of the deeper intellectual problems. They must, therefore, somehow create a new brain-quality, or organic formation of brain, capable of a mode of vision or insight impossible in their present state. They must learn somehow to remake their own brain-tissues upon a new plan. With this aim, and partly through unwitting jealousy of the natural and more balanced species which had created them, they began to use their captive specimens of that species for a great new enterprise of research into the nature of human braintissue.
Source: tatoeba (8877483)