TOES OF BIRDS. 



29 



Numher of the Digits, or Toes. 

 Birds have usually four toes, never more ; in some cases only three ; in the 

 Ostrich alone two. These are designated the first, second, third, and fourth. 

 The one attached to the accessory metatarsal bone, and which is almost always 

 directed backwards, being called the first, or hallux. The second toe, the inner 

 one of those that turn forwards, has normally three phalanges. The third has 

 four phalanges, and is the middle toe of those that are usually directed forwards. 

 The fourth has five phalanges, and is the outer toe. 



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i-^:bi4ix 



31. Red Jungle-Fowl (Gray). 



Reduction from the normal number of Toes. 



When one of the four normal toes is absent it is almost always the first, or 

 hallux, which may be entirely suppressed or exist in a rudimentary condition 

 the bones being present, but concealed beneath the skin. 



It is not always the hallux which is absent in three-toed birds. In the King- 

 fishers of the genera Ceyx and Alcyone the hallux is well developed; but the 

 second digit is reduced to its basal phalanx, appearing externally merely as a 

 wart-like eminence. 



In the Passerine genus Gholornis the fourth, or external, digit is in a rudi- 

 mentary condition. 



In the Ostrich two digits only are present, which represent the third and 

 fourth of the normal foot. The small size of the latter, and the frequent absence 

 of its nail, indicate a tendency to reduction to a single toe (the third), as in the 

 Horse among Mammals. 



Supernumerary digits. 



The conditions of the feet above shown are not departed from among birds in 

 a state of nature, except in individual variations. Under domestication, however, 

 such variations may be perpetuated in particular races, as in the Dorking Fowl, 

 a breed characterised by the constant presence of a supernumerary toe upon, each 

 foot (Nat. Hist. Museum). 



Variation in the number of Phalanges. 



The normal number of phalanges being, as shown above, 2, 3, 4, 5, in the 

 respective digits counting from the first, or hallux, to the outer toe, the following 

 variations are met with : — 



(i.) In the Tubinares (Petrels) the number of joints of the hallux is reduced 



