16 



HISTORY OF 



their time, and a new set take place, more bril- 

 liant and beautiful than the former. They add, 

 that it mends the bird's singing, and increases its 

 vivacity; but it must not be concealed, that 

 scarcely one bird in three survives the operation. 

 The manner in which nature performs this 

 operation of moulting is thus : the quill or fea- 

 ther, when first protruded from the skin and 

 come to its full size, grows harder as it grows 

 older, and receives a kind of periosteum or skin 

 round the shaft, by which it seems attached to 

 the animal. In proportion as the quill grows 

 older, its sides, or the bony pen part, thicken, 

 but its whole diameter shrinks and decreases. 

 Thus, by the thickening of its sides, all nourish- 

 ment from the body becomes more sparing ; and, 

 by the decrease of its diameter, it becomes more 

 loosely fixed in its socket, till at length it falls 

 out. In the mean time, the rudiments of an 

 incipient quill are beginning below. The skin 

 forms itself into a little bag, which is fed from the 

 body by a small vein and artery, and which 

 every day increases in size till it is protruded. 

 While the one end vegetates into the beard or 

 vane of the feather, that part attached to the skin 

 is still soft, and receives a constant supply of 

 nourishment, which is diffused through the body 

 of the quill by that little light substance which 

 we always find within when we make a pen. 

 This substance, which as yet has received no 

 name that I know of, serves the growing quill as 

 the umbilical artery does an infant in the womb, 

 by supplying it with nourishment, and diffusing 



