84 TYPES OF ANIMAL LIFE 



dexterous " manipulation " is needed to construct the 

 wonderfully delicate, yet strongly woven nests so many 

 of them form I But as they have no hand to use, and 

 cannot (as monkeys can) use their feet as hands, they are 

 forced to manage another way. And they do manage 

 admirably with the help of their bill, which is indeed a 

 " handy " organ and serves as a most skilful and delicate 

 instrument for prehension. But birds could not thus 

 use it if their neck was as little mobile as is our own. 

 Their neck, therefore, is very mobile — so mobile that, even 

 when it is short, the head can be turned round so as to 

 look directly over the back. The exclusive devotion of 

 the arms and hands to flight, makes it necessary for a 

 bird to devote its other limbs entirely, or almost entirely, 

 to locomotion. For this purpose the legs need to be 

 supplied with vigorous muscles, and yet every one must 

 have remarked what thin and delicate legs birds have. 

 The fact is, they have very strong and voluminous leg 

 muscles, but then they are gathered together in the 

 thighs and upper parts of the legs — near the centre of 

 gra^'ity. But though thus distant from the toes, they 

 are enabled to act upon them by the aid of long and delicate 

 cords, or tendons, which run dow^n side by side through 

 the thin parts of the legs to end in the toes, on which (by 

 the insertion of their tendons) the strong leg muscles act. 

 So complete, indeed, is the process of packing everything 

 as centrally as possible carried out, that birds even carry 

 their teeth in their stomachs instead of their mouths, 

 although Prof. Marsh has shown us that in the ''good 

 old times " there were birds who held to the ways of their 

 probable forefathers and kept their teeth in their jaws. 

 But they are not real teeth which our modern birds bear in 

 their breasts, though they answer the purposes of true 

 teeth They are small stones, which very many birdss 



