182 ANIMAL ACTIVITIES. 
saliva which holds the fly a prisoner until the jaws 
close over him. The ease and quickness with which 
an insect disappears are 
always a surprise to the 
observer. 
When feeding on large 
animals the frog seizes his 
prey with jaws and front 
legs, and hurriedly crowd¬ 
ing his luckless victim into 
his mouth, swallows him 
alive. Teeth are present 
on the upper jaw and on the 
palate or roof of the mouth. 
Taking Oxygen. When the young frog emerges 
from the egg it takes air from the water by means of 
external gills. Into these the blood is pumped directly 
from the heart, as in fishes. Here the oxygen passes „ 
into the blood for purification, and thence is conveyed 
to all parts of the body. 
In a few days these external gills disappear, and 
other gills grow under the opercular membrane. This 
Fig. 135.—Tongue of a Frog. 
Fig. 136.—A Young Tadpole Showing External Gills. 
membrane is joined to the body-wall except on the left 
side, where an opening for the passage of water remains. 
The young frog now breathes like a fish. The 
