xiv PROOFS OF ORGANISING MIND 289 



elastic, horny plates set close together on each side of 

 the midrib of the feather, and pointing obliquely outwards ; 

 while the barbules are to the barbs what the barbs are 

 to the feather excessively delicate horny plates, which 



MAGNIFIED VIEW OF THE BARBS AND BARBULES FORMING THE WEB 

 OF A BIRD'S WING-FEATHERS (X5o) 



FIG. 108. View of a portion of two adjacent Barbs (B, B), looking from 

 the Shaft towards the edge of the Feather. 

 bd, distal barbules ; bp t proximal barbules. 



FIG. 109. Oblique Section through the Proximal Barbules in a plane parallel 



to the Distal Barbules of the upper Figure. 



Letters as above ; I, 2, 3, barbicels and hamuli of the ventral side of the distal 



barbule ; 4, barbicels of the dorsal side of the same, without hamuli. 



(From Newton's Dictionary of Birds.) 



also grow obliquely outwards towards the tip of the barb. 

 Laterally they touch each other with smooth, glossy surfaces, 

 which are almost air-tight, yet allow of such slight motions 

 as may be required during use, while remaining interlocked 

 with the barbules of the adjoining barb in the manner just 

 described. They are the essential elements of the feather, 

 on which its value both for flight and as a protective clothing 



U 



