Page:Popular Science Monthly Volume 11.djvu/615

Rh with the perfecting of the senses. In creatures of comparatively advanced organization there arise powers of adjusting inner relations to outer relations that are far too remote for direct perception. The motions by which a carrier-pigeon finds its way home, though taken a hundred miles away, cannot be guided by sight, smell, or hearing, in their direct and simple forms. Chased animals, that make their way across the country to places of refuge out of view, are obviously led by combinations of past and present impressions which enable them to transcend the sphere of sense. And thus also must it be with creatures which annually migrate to other lands.

In man, this secondary process of extension is carried still further, Though the correspondences he effects by immediate perception have a narrower range than those of some inferior creatures, and though in that species of indirect adjustment just exemplified he is behind sundry wild and domesticated animals, yet, by still more indirect means, he adjusts internal relations to external relations that are immensely beyond the appreciation of lower beings. By combining his own perceptions with the perceptions of others as registered in maps, he can reach special places lying thousands of miles away over the earth's surface. A ship, guided by compass, and stars, and chronometer, brings him from the antipodes information by which his purchases here are adapted to prices there. From the characters of exposed strata he infers the presence of coal below, and thereupon adjusts the sequences of his actions to coexistences a thousand feet underneath. Nor is the environment through which his correspondences reach limited to the surface and the substance of the earth. It stretches into the surrounding sphere of infinity. It was extended to the moon when the Chaldeans discovered how to predict eclipses; to the sun and nearer planets when the Copernican system was established; to the remoter planets when an improved telescope disclosed one, and calculation fixed the position of the other; to the stars when their parallax and proper motion were measured; and, in a vague way, even to the nebulae when their composition and forms of structure were ascertained. At first sight, no two things could seem to have less in common than the tendency of a sprouting potato to grow toward the light, and the preparations made by human beings for such a rare, and distant, and complicated event as a transit of Venus; yet each is, objectively considered, an adjustment of internal relations to external relations, and the two phenomena are so well connected by intermediate forms that there can be no doubt of their relationship.

Physiologists are gradually proving the statement that these and all other vital changes are, in ultimate analysis, changes in the protoplasm of the body, and that they are not brought about by any peculiar vital force, but are the direct outcome of the physical and chemical structure of the protoplasm itself; so that vital changes, considered