BATRACHIA 



upper and lower eyelids of the same thickness ? With 

 which lid does it wink ? Close its eye ? 



Observe the large oval ear drum or tympanum. What 

 is its direction from the eye? (Fig. 251.) The mouth? 

 Is there a projecting ear ? Does the frog hear well ? 

 What reason for your answer ? As in the human ear, a 

 tube (the Eustachian tube) leads from the mouth to the 

 inner side of the tympanum. 



How many nostrils ? (Fig. 251.) Are they near to- 

 gether or separated ? Large or small ? A bristle passed 

 into the nostril comes into the mouth not far back in the 

 roof. Why must it differ from a fish in this ? 



How do the fore and hind legs differ ? How many toes 

 on the fore foot or hand ? On the hind foot ? On which 

 foot is one of the toes rudimentary ? Why is trie fore limb 

 of no assistance in propelling the body in jumping ? Do 

 the toes turn in or out? (Fig. 250.) How does the frog 

 give direction to the 

 jump? What would 

 be the disadvantage 

 of always jumping 

 straight forward 

 when fleeing? Which 

 legs are more useful 

 in alighting ? 



Divisions of the 

 Limbs. Distinguish 

 the upper arm, fore- 

 arm, and hand in the 

 fore limb (Figs. 252 and 253). Compare with skeleton of 

 man (Fig. 399). Do the arms of a man and a frog both 

 have one bone in the upper arm and two in the forearm ? 

 Both have several closely joined bones in the wrist and 



FIG. 252. SKELETON OF FROG. 



