HAIR, FEATHERS, AND HORNS. 147 



however, certain that the quills of the porcupine 

 present a striated appearance, having alternate bands 

 of black and white, while their pith is white ; and 

 the spines of the hedgehog are connected to the skin, 

 by little colourless bulbs, being themselves brown. 

 On the other hand, we must remember that there is 

 an intimate connexion between the colour of the hair 

 and that of the mucous web, as is observed in spot- 

 ted animals. But it is perfectly accordant with rea- 

 son to suppose this colour a secretion of the vascular 

 portion, and yet capable of being incorporated with 

 the horny covering. In most animals hair is renewed 

 annually, and in all readily reproduced. It resists 

 putrefaction longer than any other animal matter. 



Feathers are, in their mode of growth, situation, 

 and purpose, nearly related to hair ; they are peculiar 

 to birds, and may be said to consist of the quill, the 

 shaft, and the web. The quill arises like hair, 

 in the cellular membrane, and perforates the other 

 layers by a tubular opening ; it is at first membran- 

 ous and filled wath a pulp inclosed in cells, which 

 is afterwards absorbed. At the point of union with 

 the shaft there is a small hole in the middle of the 

 under side. The shaft consists of a cuticular layer 

 of matter similar to the substance of the quill ; and 

 a central portion, of a white colour, and in texture 

 resembling cork or pith ; the outer side is slightly 

 convex, the inner nearly flat, with a groove in the 

 middle, and tapering to a point at the further extre- 

 mity. There is usually a single shaft to each quill ; 

 but sometimes two, as in the southern ostrich ; and 

 in a young ostrich which had just quitted the egg 

 Blumenbach found as many as twenty proceeding 

 from a single barrel. The web generally occupies 

 both sides of the shaft, and consists of the barbs, 

 which lie over each other like the leaves of a book ; 

 and in the same manner are the sides of each barb 

 furnished with barbules. Feathers vary exceedingly 

 in appearance, being in particular parts hairy, in 

 others downy. The feathers of nocturnal birds are 



