!62 ANIMAL BIOLOGY 



ments in breathing. Can you find how often it breathes 

 per minute ? Place hand under the bird's wing. What 

 do you think of its temperature ; or better, what tempera- 

 ture is shown by a thermometer held under its wing ? Do 

 you see any connection between the breathing rate and the 

 temperature ? Test (as with the crayfish) whether a bird 

 can see behind its head ? Notice the movements of the 

 nictitating membrane. Does it appear to be transparent ? 

 Watch a bird fly around a closed room and review the 

 questions on Control of Flight. 



Bend a bird's leg and see if it has any effect upon its 

 toes. Notice a bird (especially a large fowl) walk to see 

 if it bends its toes as the foot is lifted. Pull the rear 

 tendon in a foot cut from a fowl for the kitchen. Does 

 the bird have to use muscular exertion to grasp a stick 

 upon which it sits ? Why, or why not ? When is this 

 bending of the toes by bending the legs of special ad- 

 vantage to a hawk ? To a duck ? A wading bird ? Why 

 is a fowl safe from a hawk if it stands close to a tree ? 



Do you see any signs of teeth in the bird's jaws? Why 

 are duck's " teeth " (so called by children) not teeth ? 



Can the tongue of a bird be 

 pulled forward ? (Fig. 303.) 

 What is its shape ? If there 

 is opportunity, dissect and 

 study the slender, bony 

 (hyoid) apparatus to which 

 v the base of the tongue is 

 FIG. 303. -HEAD OF WOODPECKER. attached ( F *g- 3<>3), the open- 



c, tongue; a, t,d, hyoid bone; e, f, wind- m S ^ tnG windpipe, Or 



pipe: /.salary giand. trachea, the slit-like opening 



of windpipe which is so narrow as to prevent food falling 

 into the windpipe. 



