Tails 



40^ 



shall find many unexpected uses to which the tail is put, 

 and yet those which have been explained are a mere frac- 

 tion of the problems which still await solution. 



The principal use of the tail-feathers in birds is, of 

 course, to perform the function of a rudder, and we find 

 that the arrangement of the bones perfectl}- carries out 

 the simile of a tail to the rudder of a ship; namely, a 

 broad, expanded surface which is closely hinged to the 



ViG. 320. Fig. 321. 



Tail of Barn Swallow, closed (320) and spread (321). 



body by several movable joints. The real tail of a bird 

 is the small, fleshy protuberance which in oia" roast 

 chicken we call the "pope's nose"; but in conunon jxir- 

 lance the word tail has come to be applied to the large 

 feathers which sprout from this structure. Thus, although 

 not comparable to tlie appendages of mammals, the so- 

 called tail of a bird is superficially more like the corresj^ond- 

 ing organ of a whale than the tail-fin of a fish, since it is 

 expanded horizontally instead of vertically. 



