264 



ROUND THE YEAR 

 but only hooked together by the 



interwoven, 

 barbules. 



It now becomes necessary to employ the microscope. 

 Cut out a small piece of the vane, soak it in alcohol to 

 expel the air, then transfer it to glycerine, and tease it 

 out with needles. 



We shall then find that the barbs are shaped 



FIG. 63. Part of a feather, showing two barbs and a number of barbules, slightly 

 separated. The hooks of the distal barbules grasp the proximal barbules of the 

 next barb. 



like knife-blades, the back of the blade being turned 

 outwards, away from the body of the bird, and 

 towards the convex side of the quill. Each barb 

 bears a double row of barbules, some hundreds in 

 number. Since the barbs run outwards from the 

 shaft, and the barbules outwards from the barbs, the 

 barbules will be approximately parallel to the shaft. 

 They are only approximately parallel, for they cross 

 one another at a quite appreciable angle. We must* 

 now distinguish the two sets of barbules borne upon 

 every barb. There is one set which points towards 



