Page:Popular Science Monthly Volume 25.djvu/739



VER since the study of human anatomy has attracted any attention, variations in the arrangement of the different structures of the body have been noticed. For many centuries, the signification of these variations was not understood; and even as lately as 1840, Dr. Knox, of Edinburgh, who had the courage to state his conviction that they connected man with the lower animals, was looked upon, even by members of his own profession, as one prompted by the evil-one. In early times, when great prejudice existed against the dissection of human bodies, and animals, such as monkeys, dogs, cats, etc., were frequently used as substitutes, the similarity of some of their muscles to those which occasionally occurred in man as anomalies, forced the anatomists to remark on them as being curious coincidences, though in their published works they drew no conclusions from their occurrence bearing on the origin of man.

In the view of our present knowledge of the animal kingdom and its development, and with the acceptance of the great principle of evolution, the explanation of these variations is simple enough, viz., that they point to the fact that man has descended from some lower form, and "is the co-descendant with other mammals of a common progenitor" (Darwin).

Again, many structures which in man are merely rudiments and quite useless, nay, sometimes a source of danger, are seen fully perfected in some of the lower animals, and in them fulfill a definite purpose. The existence of such rudimentary organs (or, as Haeckel calls them, "worthless primeval heirlooms") as the ear-muscles, the appendix vermiformis in the intestines, the thyroid gland, the remnant