102 ANIMAL SKETCHES. CHAP. 



the shoulder joint. In the manatee however, though the 

 arm is paddle-shaped it is capable of free motion at the 

 shoulder, at the elbow, and at the wrist. The arm and 

 fore-arm are not so much shortened, nor the fingers so 

 much lengthened, and there are flattened nails to three of 

 the digits. 



But is it not a wonderful and interesting fact that in 

 the arm of man, in the leg of a horse, in the wing of the 

 bat, in the very different wing of the bird, in the flipper of 

 the seal, and in the paddles of the manatee and the whale, 

 we can recognize the same parts in all cases an arm, a 

 fore-arm, a wrist, and a " hand " though they have been 

 so strangely and beautifully modified and adapted to the 

 special part they have to play according to the mode of 

 life of the creature that possesses them ? In some lizards 

 the arm is so reduced in size as to be quite small and use- 

 less, while in the snakes there is no arm at all. And all 

 this that is true of the fore-limb is also true of the hind- 

 limb. Always, where the limb exists, there is the thigh, 

 the shank, the ankle and the foot. But in both whales 

 and sirens the hind-limb is wanting. There is however in 

 both, near the root of the tail, a bony remnant of the hip- 

 girdle to which a very rudimentary hind-limb is attached 

 in some whales. 



You will notice that the manatee quite easily maintains 

 a horizontal position in the water ; so too do the whales ; 

 and so do the fishes. Now if you open a cod fish you will 

 find, lying beneath the back-bone, a tough bag full of air 

 or gas. This is the swim-bladder the " sound " it is called 

 when the cod fish is brought to table. It is in the best 

 position to act as a float and keep the creature right way 

 upwards and horizontal. There is no swim-bladder in the 

 whales and sirens, but the lungs extend backwards beneath 

 the backbone in a somewhat similar way. In most crea- 



