108 PRACTICAL ZOOLOGY. 



barbules. With a lens examine the upper and lower 

 surfaces of the vane; then tear one of the barbs loose 

 from the barbs in front of and behind it, and study it 

 carefully ; again watch closely while tearing two barbs 

 apart, to see how the barbules are related to each 

 other; now examine the vane of the same quill at the 

 very beginning of the vane, near the end that was 

 attached to the wing. What is the difference between 

 the arrangement of the barbs in these two places? 

 Observe the hole in the tip of the shaft; run the 

 point of a dissecting-needle along the groove in the 

 under surface of the shaft toward the base of the shaft. 

 This should lead the point of the needle into another 

 opening, communicating with the cavity of the shaft. 

 Examine this region with a lens, and determine that 

 the two sides of the vane meet at this point. Make 

 drawings of a quill, as seen from above and below, 

 showing all these points. 



With sharp scissors cut across the middle of the 

 quill. Look at the cut end ; observe that the vane is 

 attached to the upper edges of the shaft; compare 

 the place of attachment of the vane to the shaft, 

 with the place of attachment of the wing to the body. 

 Cut part of the wider side of the vane, at right angles 

 to the barbs; with a lens, or a low power of the 

 microscope, examine the edge of this cut. Make 

 drawings showing these arrangements of the parts of 

 the quill. What are the advantages of such arrange- 

 ment? 



2. Take one of the body-feathers, and compare it with 

 the quill. In what lies the chief difference ? 



3. Find a feather that is wholly composed of " down," if 



