20 The Bird 
A list of all the structures of animals which are prod- 
ucts of the outer layer alone would be a long and sur- 
prising one, and we would be very ready to grant the 
importance of skin. Such an enumeration would include 
all claws and talons, nails and teeth, the rattles of a 
snake, spurs, hairs, the scales of fishes and reptiles, 
Fic. 9.—Tarpon-scale, shark-tooth, and peacock-feather; showing diversity of 
structure derived from the skin alone. 1/2 natural size. 
spines, whalebone, beaks and feathers. Even the horn 
of a rhinocerus is only a solid mass of agglutinated 
hairs, while as the antithesis to this may be mentioned 
all down and feathers: the tiniest fluff from a humming- 
bird to the great pinion of a condor. 
If we examine a newly hatched dove or sparrow, 
the little, ugly, sprawling creature, at first glance, seems 
