18 THE STRUCTURE AND LIFE OF BIRDS chap. 



postaxial. But if we look for the bird's tarsals they 

 are not to be seen. The disappearance of the nearer 

 row is to be accounted for in this way : the bone we 

 have just called the Tibia is really the Tibia plus the 

 nearer row of tarsals which have been fused with it, and 

 its proper name is Tibio-tarsus (TT, fig. 2). This has 

 been made out clearly in the leg of the embryo bird. 

 The farther row of tarsals has also no separate ex- 

 istence. They have been fused with the Metatarsals. 

 In the young chick each row of tarsals has one large 

 separate bone to represent it. In the mature bird, 

 directly below the Tibio-tarsus comes another long 

 compound bone, the Tarso-metatarsus. At the farther 

 end of this, deep grooves show that it is made up of 

 three bones — the second, third, and fourth metatarsals. 

 Of the first metatarsal there is only the afore-mentioned 

 remnant (MTi). All these things are very difficult to 

 remember. One plan is to go over them again and 

 again till in time they become familiar. A better plan 

 is to remember the names Tibio-tarsus and Tarso- 

 metatarsus, which explain the most difficult points. 



The four digits or toes possessed by most birds are 

 the first, second, third, and fourth. The " great toe " 

 is dwarfed by the others, and has only two phalanges ; 

 the second has three, the third four, the fourth five. 

 Thus the numbers run in regular progression — 2, 3, 4, 

 5. In lizards the five toes, each attached to its 

 independent metatarsal, are always present, and they 

 have respectively 2, 3, 4, 5, 3 or 4 phalanges. The 

 correspondence in numbers is very curious. No bird 

 has a fifth toe. Domestic fowls, Dorkings especially, 

 often have a supernumerary " toe," which is really a 



