330 
LIFE, IIs T ITS HIGHER FORMS. 
versatile than those of the Apes, are capable of executing 
by their skill or power the wonderfully various require- 
ments of his reason. Finally, the anterior members of 
the "VV hales, which, as has been already observed, are all 
that they possess, are mere swimming fins, the bones of 
the toes being imbedded in a dense and leathery skin, which 
reveals no trace of their individual form or division. 
The body in the Mammalia is covered more or less 
densely with hairs, which, if less elaborate and complex 
than the feathers of Birds, aro still interesting in their 
structure. A hair is a long pointed cylinder of horny sub- 
stance, formed within a minute cavity on the surface of 
the body, and growing by continual additions to its base. 
The cavity is lined by a reflection of the common skin, and 
contains a vascular pulp well supplied with nerves and 
blood-vessels. From the surface of this pulp the horny 
substance of the hair is socreted, which, perpetually in- 
creasing from below, pushes upward the portion already 
formed, and thus increases in length. 
\ arious are the appearances,” observes Professor Jones, 
' aud widely different the uses, to which epidermic appen- 
dages, in every way analogous to hair, both as relates to 
their composition and mode of growth, may be converted • 
the wool of the Sheep, the fur of the Rabbit, the spines of 
the Hedgehog, the quills of the Porcupine, the scaly cover- 
ing of the Manis, and even the armour that defends the 
back of the Armadillo, are all of them but modifications of 
the same structures, adapted to altered conditions, under 
which the creatures live. Even the horn upon the snout 
of the Rhinoceros is but an agglomeration of hairy fila- 
ments formed upon a broad and compound pulp. The 
