WING OF BIRDS. 581 



tion is built up in succession, and in proper 

 order. Nature's next care is to construct the 

 vane, which is the part of the feather most es- 

 sential to its office : and then to form the shaft, 

 to which the vane is to be affixed, and from 

 which it receives its support : lastly, she forms 

 the barrel of the quill, which is prolonged for the 

 purpose of converting it into a lever of sufficient 

 length for the mechanical office it has to perform. 

 In proportion as each structure is finished, she 

 neglects not to remove the scaffi)lding which had 

 been set up as a temporary structure ; the mem- 

 branes, with all their partitions, are carried away, 

 the vascular pulp of the bulb is absorbed, and 

 its place supplied by air, thus securing the 

 utmost lightness, without any diminution of 

 strength. Is it possible for any rational mind, 

 after meditating upon these facts, to arrive at the 

 persuasion that they are all the mere results of 

 chance ? 



Several circumstances remain to be noticed 

 respecting the structure and actions of the wings 

 of birds. If we attend to the mode of their arti- 

 culation with the scapula, we find it producing 

 a motion oblique with regard to the axis of the 

 body, so that the stroke which they give to the 

 air is directed both downwards and backwards ; 

 and the bird, while moving forwards, is at the 

 ^me time supported in opposition to the force of 



