VESTIGIAL ORGANS
lutionary change certain organs might naturally lose their usefulness and be replaced by others of a more appropriate type. As such organs gradually decay, so to speak, they should be expected to appear in much the way that vestigial organs do. Man possesses a system of functionless muscles connected with his external ear because these muscles were once useful to that organ in a pre-human ancestor who had occasion to move his ears as some modern animals still do. Man has a hairy covering before birth in consequence of his derivation from a stock of animals once fully covered with hair. His vermiform appendix is the remnant of an organ that was once a functional part of the digestive system of a remote ancestor.
Like other animals, man is not only a highly equipped and efficient organism with a most marvelous system of parts adapted to serve his bodily needs but he is also a repository of some of the most interesting and important relics of the past, relics whose significance can be truly understood only if they are viewed from the standpoint of the evolutionist. These relics are vestigial organs, and it is in this way and in this way only that such organs can be understood.
Organic evolution is not a principle that is open to direct and simple proof. Like the movement of the earth around the sun it can be demonstrated only indirectly. We do not even know that the earth is round by direct inspection. The shadow cast by the earth on the moon in an eclipse, the appearance of the ship as it rises over the horizon, and a number of other occurrences in nature are best explained on the assumption that the earth is round. The Copernican theory explains astronomic phenomena, it accounts adequately for all happenings in the skies. In a similar way organic nature, plants as well as animals, is full of happenings that call for some general explanation, and no principle
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