THE FOOT. 17 



In descriptive ornithology, the foot, or that part of 

 the limb between the heel and the toes, is commonly 

 called the tarsus. In some cases, as those of most 

 Owls, it is clothed with feathers like the leg ; it is or- 

 dinarily, however, covered with horny or leathery in- 

 tegument resembling that of the bill, and this hard 

 skin is usually broken up into a number of scales or 

 plates, the arrangement of which has been found of 

 importance in classification. 



The number of toes in most birds is four ; there 

 are never more ; sometimes there are but three, and 

 the Ostrich has but two. There are usually three in 

 front and one behind ; sometimes, as in the Wood- 

 peckers and Cuckoos, there are two before and two 

 behind ; very rarely all four toes point forward. When 

 there are but three toes, the hinder is always the miss- 

 ingr one. A bird's toes are numbered from one to four, 

 the hind toe being the first, then the inner front toe, 

 next the middle front toe, and lastly the outer front 

 toe. These digits are connected together by complete 

 or partial webs in swimming and many wading birds ; 

 and they usually bear well-formed, arched, and acute 

 claws, corresponding to the claws, nails, or hoofs of 

 quadrupeds. The many modifications of the feet, like 

 those of the bill, serve in large measure to distinguish 

 different groups of birds. 



The part of a bird's hind limb called the tarsus con- 

 sists of several originally distinct bones, which more or 

 less completely fuse together in adult life. The toes, 

 on the contrary, retain the mobility of the several joints 

 of which they are composed ; and, as a rule, the hind 

 toe has two joints, the inner front toe three, the middle 

 front toe four, and the outer front toe five. 

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