XVII 
THE CROCODILE 
215 
in 
The respiratory mechanism of the crocodile is arranged 
a cunning way to suit the requirements of a 
rapacious reptile which obtains its prey in the water, 
for terrestrial animals secured by these brutes are 
dragged under water and drowned. Crocodiles breathe 
by means of lungs which, as usual, communicate with the 
nasal passages by means 
of a windpipe (trachea) 
of the usual construction. 
Their nostrils are on the 
upper surface of the 
broad snout and appear 
as a pair of slits : each 
nostril is guarded by an 
oval sphincter which 
enables them to open 
and close the nostrils at 
will exactly as other 
animals can open and 
close their eyelids. I 
have not been able to 
satisfy myself that a 
crocodile can close one 
nostril independently of 
the other, as is the case 
with the eyelids in the 
act known as winking 
with one eye. 
The tongue of the 
crocodile is thick, flat, 
and so fixed to the floor 
of the mouth that it 
cannot be protruded. The hinder margin of the tongue 
is raised into a transverse fold which meets the soft 
palate and shuts off the cavity of the mouth from the 
pharynx. This arrangement enables the crocodile to 
lie completely submerged in water with only the nostrils 
exposed and respire freely without any risk of water 
Under surface of the head of a young 
crocodile showing the openings of the 
musk gland. 
