THE ENGLISH SPARROW 83 



to the dorsal side of the body so that in flight the body 

 hangs suspended. Find three principal joints in the wing. 

 Note the long quill feathers in each wing and in the tail. 

 Allow a bird to fly about the room and observe the move- 

 ments of the wings. Also note that the tail is used as a 

 rudder in guiding the bird, and as an aid in alighting. 



Note that the head is prolonged into a horny beak, com- 

 posed of the upper and lower mandibles. At the base of 

 the upper mandible are the nostrils. Note where they open 

 into the mouth. Note the bristles hanging at the corners 

 of the mouth. These are the rectal bristles. 



Note the large eyes. How many eyelids have they? 

 Note the membrane that can be drawn wholly over the eye. 

 This is the nictitating membrane. 



(Some of the above features can be best observed on a dead bird. 

 When necessary kill the bird by holding a piece of cotton saturated 

 with chloroform to its nostrils.) 



Below and behind the eye, look for the ears. They are 

 hidden by the feathers. There are no external ears, but 

 the auditory openings may be found. The feathers over 

 the openings are not so compact as elsewhere. Why ? 



Feathers. Examine a feather in detail. Note the shaft 

 running through the center. The lower, transparent, hol- 

 low part is the quill. It extends only to the wide, expanded 

 portion, the vane. The remaining part of the shaft, in the 

 middle of the vane, is the rachis. Note that the rachis 

 is opaque and solid. In the lower end of the quill, note an 

 opening. A small conical projection of the skin fits into 

 this opening, when the feather is attached to the body. 

 Observe the vane closely. It is made up of narrow, linear 

 plates, running out to the right and left from the rachis. 

 These are the barbs. The barbs are fringed with similar 



