Page:Creation by Evolution (1928).djvu/73

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VESTIGIAL ORGANS

it is now customary, as an incidental step in many abdominal operations, to remove the appendix on the assumption that a person is better off without it than with it. There is no reason to suppose that the appendix in man performs any function whatever, and since its removal is unattended by any subsequent inconvenience, it is commonly set down as a useless organ.

Fig. 7.—A, Cæcum and appendix of a rabbit, showing the small intestine entering from above and the large intestine emerging to the left; B, Similar parts in man, with the vestigial vermiform appendix to the right.

In other mammals than man the vermiform appendix or its equivalent presents a variety of conditions. It is not always easy in these lower forms to distinguish the exact limits between caecum and appendix, but in the rabbit, for instance, a large and highly complex caecum communicates freely and easily with an extended and apparently highly functional appendix. Without doubt these two parts are of great value in the digestive functions of this mammal, and the same may be said of them in many other animals. They are both greatly reduced, however, in the monkeys and in the anthropoid apes, where they are represented by a condition almost exactly like that in human beings. In consequence of the state of the vermiform appendix as seen in man it may be set down in the human species as a truly vestigial organ.

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