XVII 



THE CROCODILE 



215 



The respiratory mechanism of the crocodile is arranoed 

 in 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 apjjear 

 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 winkine; 

 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 comjjletely 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. 



