CREATION BY EVOLUTION 



If we examine the angle of a cat's eye corresponding to 

 the nasal angle in man we shall see there not a small fold 

 of membrane but a veritable third eyelid. This additional 

 lid may be made to pass under the two outer lids and over 

 the whole exposed surface of the eyeball in a way to sweep 

 this surface completely. It is provided with muscles by which 

 this movement is quickly and easily made. This nictitating 

 membrane, as it is called, is well developed in most mam- 

 mals and serves to protect the eye. In man its representative 

 is the insignificant fold already described, which, devoid of 

 muscles and other appurtenances, is in its present condition 

 a purely useless part, a vestigial organ. It is a noteworthy 

 fact that, though the nictitating membrane is a functional 

 organ in many mammals, it is reduced to a semilunar fold 

 not only in man but in the monkeys and the apes. 



Vestigial organs in man are found not only on the exterior 

 of the body, as shown by the eye and the ear, but in its 

 interior. In human beings the small intestine is not con- 

 tinuous with the large one end to end, but the small intestine 

 enters the side of the large intestine, the natural termination 

 of which is a pocket that projects backward and is known 

 as the caecum. This pocket carries on its surface a small 

 worm-like attachment, the so-called vermiform appendix, 

 whose cavity opens directly into that of the caecum. In a 

 way the vermiform appendix marks the real ending of the 

 large intestine (Fig. 7). As is well known, the appendix 

 readily becomes a center of intestinal disturbance and is the 

 seat of the disease known as appendicitis, the usual surgical 

 cure for which is to remove the appendix. Thousands of 

 human beings have had the appendix removed and con- 

 tinue to live without experiencing any inconvenience. In 

 fact, their position in life after the removal of this trouble- 

 some organ is so much more secure than it was before that 



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