148 



WHALES 



Figure öj. I^ft view 

 of the larynx of a 

 horse, a Rorqual, 

 a Narwhal and 

 a Pilot Whale. 



E = epiglottis; 



T = thyroid carti- 

 lage; 



C = cricoid carti- 

 lage ; 



A = arytenoid 

 cartilage ; 



D = diverticulum. 



n }) 



point of entry into the throat, i.e. where the beak-shaped cartilage 

 protrudes into it (Fig. 86). As a consequence, there exists a much more 

 direct connexion between the nose and the trachea than is found in 

 terrestrial mammals and Mysticetes and, moreover, air is prevented 

 from entering the mouth during exhalation, and water from entering the 

 trachea during inhalation. The system works particularly efficiently since 

 the specially thickened walls of the throat are provided with annular 

 muscles which act as a tight ring round the 'beak'. This ring is not easily 

 dislodged by movements of the throat or the epiglottis, mainly because 

 the beak, as we have seen, is equipped with a stud at its tip. In Sperm 

 Whales and Pigmy Sperm Whales the beak does not lie in the centre but 

 a little to the left, so that the left passage to the oesophagus becomes 

 narrower and the right passage wider. It was formerly believed that this 

 was due to the fact that Sperm Whales swallow their food in large gulps, 

 but considering that Killer Whales swallow seals whole and yet have a 

 central 'beak', this explanation must be discarded. The phenomenon is 

 probably associated with the asymmetrical blowhole position of Sperm 

 W^hales and related species. 



While the peculiar beak and the associated structures provide a 



