114 The ^Iam.mals. 



of life. In the whales these hairs may. however, he re- 

 duced to a few bristles in the region of the mouth, which 

 disappear when the animal attains maturity. ^Mammals 

 never develop that modified kind of hair-structure known 

 as feathers. Avhich are peculiar to Birds. The body may, 

 however, be covered with overlapping scales, like those 

 so common in Reptiles, but this occurs only in the pan- 

 golins, or scaly ant-eaters of India and Africa. The tail 

 of the common rat is an example of a part of the body 

 covered with scales, having their edges in opposition; but 

 in both these instances hairs are mingled with the scales. 

 Still rarer than scales are bony plates, developed in the 

 true skin. At the present day these structures are only 

 met Avith among the well-known armadillos of South 

 America, which are furnished with bucklers and trans- 

 verse bands of these bony plates, and are in some cases 

 able to roll themselves up into a ball, presenting on all 

 sides an impenetrable coat of mail. Between the plates 

 of the armour of the Armadillos hairs are always devel- 

 oped, and in one species these are so abundant as to com- 

 pletely hide the plates themselves, and render the gen- 

 eral appearance that of an ordinary hairy mammal. 



"The use of hair is mainly to protect the body from" 

 cold, and thus to aid in the maintenance of a uniform high 

 temperature ; and when hairs are absent, we find this 

 function performed by a more or less thick fatty layer 

 beneath the skin, which, when it is excessively developed, 

 as in the Avhales, is known as blubber. To compensate for 

 the difference between the temperature of winter and 

 summer, Mammals which inhabit the colder regions of 

 the globe develop a much thicker coat of hair in the 

 former than in the latter season, of which we have an ex- 

 cellent example in the horse. In some Mammals, such as 

 the hare and cat. the body is covered with only one kind 

 of hair; but in other cases, as in the fur-seals, there is one 

 kind of long and somewhat coarse hair, which appears at 

 the surface, and another of a softer and finer nature, which 

 forms the thick and warm under-fur. This under-fur is 

 greatly developed in ^Mammals of all groups inhabiting 

 Tibet, where it is locally known as "pashm": and it is 

 this pashm of the goat of these regions which affords the 

 materials for the celebrated Kashmir shawls. Curiously 



