FEKT OF BIRDS. 517 



wholly disappeared. The long bone which suc- 

 ceeds to the tibia, though considered by some ana- 

 tomists as the tarsus, is properly the metatarsal 

 bone, and in the Grallae is of great length. At its 

 lower end it has three articulations, shaped like 

 pullies, for the attachment of the three toes : there 

 is besides, in almost all birds, a small rudiment of 

 another metatarsal bone, on which is situated the 

 fourth toe. The number of bones which compose 

 each respective toe appears to be regulated by a 

 uniform law. The innermost toe, which may be 

 compared to a thumb, consists invariably of two 

 bones: that which is next to it in the order of 

 sequence has always three; that which follows has 

 four ; and the outermost toe has five bones : the 

 claws in every case being affixed to the last joints, 

 M^hich have therefore been termed the uiioital bones. 

 This remarkable numerical relation among the 

 several bones of the toes exists quite independently 

 of their length. 



There is one whole order of birds which are par- 

 ticularly fitted for climbing and perching upon 

 trees, having the two middle toes parallel to each 

 other, and the inner and outer toes turned back, so 

 as to be opposed to them in their action. They 

 are thus enabled to grasp objects with the greatest 

 facility ; having, in fact, two thumbs, which are 

 opposable to the two fingers. They have been 

 termed Scmisores, or Zygodactyli. Almost all other 

 birds have three toes before, and one behind. 



From this enumeration it would appear as if 

 Nature, in modifying the type of vertebrated ani- 

 mals to suit the purposes required in the bird, had 

 purposely omitted one of the toes, which are usually 



