RUDIMENTARY OR VESTIGAL ORGANS 415 



just below the " knee " (Fig. 120). At the present time 

 they are of no service, and represent the last traces of two 

 fingers or toes which once were provided with hoofs and 

 were functional. 



In man there are not fewer than 170 vestigial organs. 

 The appendix, for example, is a remnant, often a trouble- 

 some one, whereas in such animals as the rabbit and 

 kangaroo it is of vital importance. There are also traces 



B 



.*£<-'£. 





Fig. 121. — Homologous Organs: A, wing of bat; B, wing of bird. 



of a tail with rudimentary muscles, muscles that once 

 moved the ears and twitched the skin, a rudimentary 

 third eyelid, such as one finds well-developed in the 

 birds, and numerous other vestiges associated with the 

 skeletal, muscular, and other systems. 



Examples of this class of organs in other animals as 

 well as in many plants could be multiplied to a great 

 length. In every instance their presence can be explained 

 on the assumption that each of these organs was func- 

 tional in a remote ancestor. Indeed, they are definitely 



