166 THE STORY OF THE BIRDS. 
But we shall see in the next chapter that when 
sudden spurts of speed are required by fluttering in a 
fluid as air or water, a shorter, rounded fanning mem- 
ber is demanded. Hence, in keeping with safety, the 
fin, foot or wing has had its outer rays, toes or quills 
shortened. Now we can, therefore, see how the newt 
to the outer toe in lizards became the longest, and 
how when the shorter fifth was lost in the birds they 
were left with their outer toe having the greatest 
number of joints. 
It is evident, however, that neither limb clasping 
or walking on a flat surface would have any tendency 
to preserve this prestige, but would tend to develop 
the middle front (or third) toe into the stronger by its 
greater use in its central position. Hence, we find its 
joints (though only four) usually lengthened and en- 
larged in perching and walking birds, until it is de- 
cidedly the most prominent. This same tendency to 
strengthen the middle toe (horse) or pair of toes (cows, 
hogs) and to lessen the size of the outer, or abolish 
them altogether (horse, antelope), is strikingly seen 
in many mammals and is an interesting study. 
Among the diving birds of long ago and in some 
low aquatic birds now the use or need of this outer toe 
to make a backward and outward paddling stroke more 
effective has brought out again the prestige of this 
outer five-jointed toe, and it is here not only the long- 
est, but very much the largest in some cases—a pos- 
sible instance of redevelopment when an old tool is 
used at an old task in an old environment. 
In the leg, above the bird’s toe, are many interest- 
