430 THE LIFE OF A BIRD. 



the ground, because the power of preserving the 

 balance has been suddenly lost to them. The 

 impossibility of our sleeping in an erect position, 

 unsupported, is a familiar fact. By the beautiful 

 manner in which the leg of the bird is formed, and 

 the exactness with which it is placed in the centre 

 of the weight, its legs, though so slight and delicate, 

 are, nevertheless, capable of preserving it steadily 

 upright. 



The wings of a bird, though less characteristic 

 than the feet, for the purposes at least of the orni- 

 thologist, are interesting parts of its anatomy. It 

 need scarcely be said that they are the representa- 

 tives of the arm and hand in man, just as in the 

 case of the legs. They consist of an upper arm- 

 bone or kumerus, of two bones forming the fore- 

 arm, analogous to that part of the human arm 

 extending from the elbow to the wrist, and the 

 lowest portion consisting of bones representative 

 of the wrist and hand in man. These bones are 

 so formed as to give them the greatest possible 

 degree of motion, combining at the same time 

 great stifihess and rigidity in their structure. And 

 when we consider the powerful and long-continued 

 muscular efforts which put them into action during 



