18 THE STRUCTURE AND LIFE OF BIRDS cuap. 
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—2z, 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 
