SKELETONS OF BIRD AND REPTILE 



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 

 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 I, 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- 



111 



between the two, 



Fig. 3- 



-Tibia and Fibula of 



Fowl, 

 fibula ; T, tibia. 



merus (HU, fig. 2) has broad- 

 ened, especially at the nearer 

 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 



