INTRODUCTORY 



13 



Vane 



Vexillum 



Magnified portion 

 of Vane 



Barb 

 Barbule 



Si second series of flattened rods, known as the barbules, so small 

 as to require the microscope to reveal them. But the mechanism 

 by which this vane is held together is so wonderful, that I venture to 

 ask my readers to bear with me while I endeavour to explain it. 



In the diagram of a feather (fig. 5) depicting the different parts, 

 you will notice on the 

 right side a small 

 portion shown as if 

 seen through a mag- 

 nifying-glass, thereby 

 roughly indicating the 

 appearance of barbs 

 and their barbules. In 

 fig. 6 a portion of 

 this magnified area is 

 shown as it appears 

 when seen in a section 

 and still furthur mag- 

 nified. You will now 

 see (fig. 6) that each 

 barb, represented bytwo 

 flattened rods seen in 

 vertical section, bears 

 two quite different 

 kinds of barbules, set 

 so that while one series 

 is cut across, the other 

 remains uninjured. 

 The reason for this 

 will appear presently. 

 The uncut series in 



this diagram are those known as the anterior radii or barbules, 

 because all point towards the tip of the feather when in their 

 natural position. Each takes the form of a ribbon-like plate 

 set slantwise into the barb (fig. 6), and having half its length 

 deeply cut, as with a fretsaw, to form a number of very delicate, 

 almost thread-like, pieces, the upper short and bearded, the under 



Fig. 5.— The Structure of a Feather, showing a 

 portion highly magnified, from a Drawing by 

 W. P. Pycraft. 



