CHAPTER XIII 



WINGS 



EFORE the front limbs of an.y creature had be- 

 come adapted to flight through the air, they 

 served to assist the hind legs in locomotion on 

 the ground, and, ages before this, a many-rayed mem- 

 brane stretched across the primitive fin, aided its owner 

 in cleaving a way through the water. So, like a palimp- 

 sest, if we look beneath the outer covering of feathers, 

 we see, in the wing of the modern bird, the three fingers 

 hinting of widely different ancestral habits. 



The general structure and appearance of the bills, the 

 feet, and wings of various birds is the result of a function 

 characteristic of each. The bills are used to procure 

 food, the feet to walk or perch, and the wings to propel 

 the bird through the air. But, as we have seen in the 

 case of the bill, these organs are put to many other uses 

 besides the one for which they were primarily adapted. 

 This is only what we should expect when we consider the 

 relative high position which avian intelligence holds, and 

 the remarkable extremes of environment with w^hich 

 these structures — bill, feet, and wings — are brought into 

 close touch. 



The photograph of the young heron's wing shows 



319 



