The mind is a very wonderful thing, but it is questionable whether it is more wonderful than some of the instinctive modes of behavior of lower forms of life. If mind is viewed as an adjustment to external conditions for the purpose of securing control, the human mind is no more wonderful in its way than the homing and migratory instincts of birds; the tropic quality of the male butterfly which leads it to the female though she is imprisoned in a cigar-box in a dark room; or the peculiar sensitivity of the bat which enables it, though blinded, to thread its way through a maze of obstructions hung about a room. The fact of sensitivity, in short, or the quality of response to stimulation, is more wonderful than its particular formulation in the human brain. Mind simply represents a special development of the quality of sensitivity common to organic nature, and analogous to the sensitivity of the photographic plate. The brain receives impressions, records them, remembers them, compares new experiences with old, and modifies behavior, in the presence of a new or recurrent stimulation, in view of the pleasure-pain connotation of similar situations in the past. In very low forms of life, as is well known, there is no development of brain or special organs of sense; but the organism is pushed and pulled about by light, heat, gravity, and acid and other chemical forces, and is unable to decline to act on any stimulus reaching it. It reacts in certain characteristic, habitual, and adequate ways, because it responds uniformly to the same stimulation; but it has no choice, and is controlled by the environment. The object of brain development is to reverse these conditions and control the actions of the organism, and of the outside world as well, from within. With the development of the special organs of sense, memory, and consequent ability to compare present experiences with past, with inhibition or the ability to decline to act on a stimulus, and, finally, with abstraction or the power of separating general from particular aspects, we have a condition where the organism sits still, as it were, and picks and chooses its reactions to the outer world; and, by working in certain lines to the exclusion of others, it gains in its turn control of the environment, and begins to reshape it.