INTRODUCTORY 



17 



Vane 



Maiii'Shaft 



'Downy "= barbs 



appear in the form of tiny bead-like bodies, which soon sink down 

 into a pit. Next an outer protecting sheath is developed around this 

 feather rudiment, and within this the mass of pulp which it contains 

 proceeds to form first the main axis, and next the barbs and barbules. 

 What will prove the tip of the feather is the first to be formed, and 

 as this forces its way up, the lower parts are added, till at hatching- 

 time the whole of the down feather is completed. 



At the base of this down feather lies the germ of the contour 

 feather which is to fol- 

 low. As this grows 

 the down feather is 

 thrust out upon the tip 

 of the new contour 

 feather, and here it 

 may be attached for a 

 very considerable time, 

 as in the case of young 

 Herons, for example. 

 On its first appearance, 

 as everybody knows, 

 the new feather is en- 

 sheathed in a thin, 

 delicate blue wrapper, 

 the first-formed por- 

 tion of the vane burst- 

 ing its way through 

 while the lower-most 



portion of the feather is yet forming. This lower portion is filled 

 with a mass of jelly-like pulp, richly supplied with blood. After 

 the feather has completed its growth, if the barrel, or " quill," of 

 the feather be cut with a sharp knife, the empty cases, or '* cells," 

 which held the pulp will be found lying one above the other in the 

 centre of the quill. 



In most birds the feathers are renewed at least once annually, 

 by the process known as moulting — a critical time in a bird's 

 life. When there is a lack of suitable nourishment, or when 

 the bird is low in vigour at the moulting-season, the feathers 



3 



After=sbaft 



Quill 



Fig. 7. 



