330 



LIFE, IX 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 Whales, 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, are 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 secreted, which, perpetually in- 

 creasing from below, pushes upward the portion already 

 formed, and thus increases in length. 



" Various are the appearances," observes Professor Jones, 

 "and 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 



