Feathers. 1 1 3 



of the hair, but takes no actual part in its formation, merely, 

 serving to bring closer the necessary blood-vessels and nerves. 



If the skin of a bird be carefully examined, there will be 

 found among the feathers thin and delicate horny shafts, 

 which have every resemblance to hairs. But between these 

 filo-plumes and the most complicated feathers, every inter- 

 mediate stage will be found ; and even the filo-plumes them- 

 selves have commonly a few slight branches at the summit. 



At its origin, however, a feather— even these simplest 

 feathers— is different from a hair. " It appears first as a slight 

 outgrowth, a papilla, of the 

 skin. This is surrounded by a 

 depression, out of the middle 

 of which the papilla arises. 



The papilla consists both of ^^^^^^^^^^^M^'-'^s 

 dermis and epidermis ; but / '^T^'^^SS'" -j^^ ' 



the epidermis alone enters " 



■ .„ tu r i- r i.\. Fig. 56.— Feather papilla. (From Gadow, 



mtO the lormation 01 the in Newton's "Dictionary of Birds.") 



feather, the dermis becoming ^. p"Ip ; e, iv., m, different layers 



I 1 1 -Till of epiderm. 



the central pulp, with blood- 

 vessels, nerves, etc. The surrounding fossa deepens, and thus the 

 developing feather comes to lie at its base within a sheath. The 

 feather itself is formed purely by a horny change in the epidermic 

 cells, which are separated into three layers. The outermost 

 layer forms a delicate sheath, which is cast off when the feather 

 is fully formed, but which may be often seen encasing a newly 

 formed feather in a moulting bird ; the middle layer forms the 

 feather itself, whose complicated form is due to the irregular 

 modification of the cells, as will be explained directly, while 

 the innermost layer of all forms that series of cup-shaped bits 

 which occur in the inside of the quill, and to which the Germans 

 have given the poetical name of " Federseele." A feather 

 itself, when most fully developed, such as one of the strong 

 remiges which fringe the wing, or rectrices which form the tail, 

 or contour feathers, as the strong feathers of the general body 

 surface are called, consists of a quill, or calamus, which is 

 hollow, and of a rhachis above this ; at the junction of the two 

 is a minute perforation, the umbilicus, and at this point a small 



