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triking illustration of increasing complexity. In the lowest forms of animal life, we find general sensibility only, and it is claimed that this exists in the lowest forms, without even the presence of nerves. But as we rise higher in the scale, the special organs of sense gradually become developed--one new sense after another appears; but this is not the only line of increasing complexity. When an organ of sense first appears, its function is of the simplest character; and it is only when we reach the highest types of animal life that it performs the greatest variety of offices peculiar thereto. That of touch is, at first, but crude and simple, becoming delicate and complicated only in the highest types. The sense of pain is a differentiated function, possessed only in a slight degree by reptiles and fishes, and probably not at all by animals still lower in the scale. The eye-spots of star fishes and jelly fishes simply distinguish light from darkness, much as we do with our eyes closed. There are many degrees of development from this condition of the inferior organism to that of the human eye, which distinguishes the nicest shades of color, distance, form, and size of objects, and the play of passion on the human countenance. The same variety of function is acquired by the ear in its development from its simplest to its most complex form. In the higher animals, the organ of hearing is formed of three parts, an external, middle, and internal portion; but in birds the external ear is wanting; in fishes both the external and middle parts are wanting; in mollusks it is reduced to a simple sack of microscopic dimensions, filled with a liquid in which there are otolithes, or pebbly substances. Such an organ can distinguish noises only; it can recognize nothing of the infinite variety of articulations, notes, tones, melodies, harmonies of the human voice and of musical instruments. There is even a great difference between the disciplined, and therefore differentiated ear of a cultured person, and the undisciplined, and therefore less differentiated ear of a boor. Similar specializations of structure and function pertain to the other senses; but we may pass them. The digestive, circulatory, and respiratory systems, and all the other systems of the animal structure, evince the same law. The lowest form of the circulating fluid, as in sponges, is simply water containing gases and organic particles; and this can scarc
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