158 NEW ZEALAND NATURE-STUDY BOOK 
The Mouth.—The mouth is wide and deep; indeed 
the whole head of the animal seems to open when the jaws 
are gaping. The upper jaw contains a row of fine teeth 
along the margin, which, like those of the fish, point back- 
wards towards the throat. In the lower jaw there are no 
teeth. 
The Tongue. The forked tongue is attached to the 
front and middle part of the lower jaw, and, when the 
mouth is closed, points back- 
wards in the same direction as 
the teeth. This arrangement 
enables the tongue to be thrown 
forward and flicked out to its 
full length. It is covered, more- 
over, with a thick slimy matter, 
which sticks tenaciously to its 
Fig.103.—Head of Frog, showing 
attachment of Tongue, andits Prey. 
action in catching Flies; also E 5 t 
Ear-drum (@). The Skin.—The skin is 
very porous, and is kept moist 
by a slimy fluid, which is constantly poured out from 
numerous small glands. The evaporation of the moisture 
serves to keep the body cool even when the weather is hot, 
a matter of the utmost importance to an animal which 
cannot live when the temperature rises beyond 100° F. 
Respiration.—Respiration takes place through the 
lungs and skin. If a resting Frog be watched, it will be 
seen to lower and raise the floor of the mouth alternately 
—this action being part of the process of breathing, which 
is carried on as follows: The mouth is closed, the floor of 
the mouth depressed, and the nostrils are opened. This 
causes air to be forced in through the nostrils, These are 
then shut, the floor of the mouth is raised, and the com- 
pressed air flows into the lungs. Here an exchange takes 
