Il SKELETONS OF BIRD AND REPTILE 9 
undergo, bones remain, relatively to each other, in the 
same position. Hence it often happens that to observe 
carefully the position of a bone is the best way to 
discover what bone it is. The wrist now follows, con- 
sisting of two rows of bones called Carpals (C, fig. 4a), 
with a central one (CE) wedged in between the two, 
after these the five Metacarpals, 
the bones of the hand (MC). 
Next to them come the finger 
bones, each division being 
called a Phalanx (D 1, 2, 3, 
4, 5). The thumb has two 
phalanges, the second digit 
three, the third four, the fourth 
five, and the fifth three. And 
at the end of each digit is a 
claw. Apart from its being 
featherless, nothing less suited 
for flying can be imagined. 
If we turn now to the bird 
we shall find that the Hu- a 
‘merus (HU, fig. 2) has broad- Fic. 3-—Tibia and Fibula of 
ened, especially at the nearer F, fibula; 1, tibia 
end, and is covered with great 
protuberances, good evidence that powerful muscles 
spring from it and are attached to it. Till we come 
to the fingers, there will be a striking increase in the 
length of the various bones. A bird’s wing would be 
an outrageously long leg for a lizard of equal weight 
and bulk. When the long radius and ulna are ex- 
tended, the elbow-joint allows of no turning motion. 
As is essential for flight, they are held stiff whatever 
