in RUDIMENTARY STRUCTURES 157 



which constitute a real, though an in- 

 visible, tail in Man, are quoted as a case 

 of a rudimentary organ. The truth is 

 that this very short tail in men is far 

 more clearly functional than many very 

 long tails in other animals. It is 

 absolutely needed for the support of the 

 whole frame when it is subjected to the 

 strain of its own weight for long periods 

 of time in the sitting posture, a posture 

 which is peculiar to Man and, in a less 

 degree, to Monkeys. It is not clear that 

 there is any functional use in the long 

 tails of dogs, of cats, and of many other 

 animals. They are, indeed, very ex- 

 pressive of the emotions, and this, no 

 doubt, is of itself a use. Perhaps more 

 really belonging to the category of rudi- 

 mental organs may be the traces which 

 are said to exist in the human head of 

 the special muscles which move the ears 

 in lower animals. If such exist, although 



