226 THE INVISIBLE WORLD 



species. Unused from generation to generation, 

 these organs gradually shrivel away to mere frag- 

 ments, finally vanish. 



In the onward evolution of Man from the higher 

 animals, with his upright position and new en- 

 vironment, he does not need certain organs needed 

 and largely used by his ancestors. Unused 

 through long generations, these organs, by slow 

 degrees, degenerate into mere rudiments, at last 

 to disappear. 



Among many others, the appendix is such an 

 organ, a mere fragment of what it once was in 

 some of Man's remote ancestors. 



When these ancestors walked on all fours, the 

 appendix was a part of the caecum, the closed end 

 of that organ. It was large and much used. But 

 when the ancestors, by evolution, assumed the up- 

 right position as man apes, and then Man, this part 

 of the caecum was needless and unused. There- 

 fore by slow degrees it shriveled up to what it now 

 is in man. It is situated low down on the right 

 side of the abdomen, wormlike, the size of a small 

 quill, with a caliber sufficient only to receive the 

 common knitting needle. One end is closed, the 

 other end is open, unites with the remaining part 

 of the caecum and, through that, with the large 

 intestine. 



In some persons the appendix, no doubt, has dis- 

 appeared. In others, it is but an inch long by a 

 quarter of an inch in diameter. In others it is 

 two inches long. In other, three; in others, four. 



