On the Sense of Feeling. 305 



The mammalia generally cast their coat at a certain season of the year, 

 and it is replaced by another. In winter the fur is usually much thicker 

 than during the warmer seasons, and possesses a larger quantity of duvet, 

 or intermediate short silky hair, which is an admirable non-conductor of 

 heat. As a general rule, the animals inhabiting cold climates possess long, 

 silky coats ; those in hot climates, short, dry, and harsh ones. 



Tiie external coverings of tiie mammalia are tlien very various. In the 

 cetacea the integument is polished and slippery, calculated for motion in 

 the water. In the sheep the wool is more or less silky : in the cow and 

 horse the hair is short. The skin of the elephant and rhinoceros is, as 

 their name of pachydermata implies, very thick j tiiat of the hog is very 

 dense, and makes, therefore, excellent saddles. The ornithorhynchus is 

 covered with short fur, the armadillo with bands of mail, the pangolin with 

 scales, tlie beaver with thick felt, the porcupine with quills, the hedgehog 

 with bristles, the monkey with hair. 



Horns are of two kinds, solid and hollow. 



Hollow horns are formed around a solid bony axis, a process from the 

 frontal bone, the horn itself being a thin shell, inorganic, and deposited in 

 conical layers. Such horns do not fall off: of this kind are the horns of the 

 ox, antelope, ram, &c. 



Solid horns are altogether different. They are formed of an agglutinated 

 mass of hair, the bulbs secreting which lie in juxtaposition below. These 

 horns are fibrous, pyramidal, are connected only with the skin, and are 

 reproduced from below, as they are worn away above. The horn of the 

 rhinoceros is of this nature. 



The scales of such of the mammalia as possess them, are formed in a 

 similar manner, the bulbs being placed in a line, or an eccentric ellipse, 

 instead of a circle ; as may be well seen in those of the pangolin, or ant- 

 eater. 



The antler of the stag is a real bony process, growing not from its base, 

 but from its extremity, covered to a certain stage of its growth with hair, 

 and it is deciduous. 



During its growth, the antler is invested by a vascular periosteum, or 

 membrane, by which it is nourished, and into which the vessels pass 

 through the osseous circle at the root. 



When an antler is completely formed, which occurs after about three 

 months, the vessels at the root contract and degenerate ; and the periosteum, 

 deprived of its nutritive fluid, peels off. 



When the animal sheds its antler, the integuments close over the de- 

 nuded bone, and thus remain until the proper season, when the same circle 

 of changes is recommenced. 



Besides the general sense of tact, which resides in a greater or less de- 

 gree over the integument of the mammalia, they arc endowed with special 

 organs of touch ,• that is, there are certain parts of their bodies, adapted 



