RESPIRATION I47 



as we know, is situated at the beginning of the trachea, and its walls are 

 supported by special laryngeal cartilages; the pharynx (throat) is the 

 intersection of the trachea and the oesophagus; and the function of the 

 nose requires no special discussion. In mammals, nasal and buccal 

 cavities are separated by a bony plate called the hard palate and its 

 continuation, the soft palate, consisting of mucous membrane and muscle. 

 In most mammals, the soft palate is rather long and extends back to the 

 region of the glottis. In this way the connexion between the naso-pharynx 

 and the larynx is kept open, and air from the nose can reach the respira- 

 tory tracts while the animal is eating. During swallowing the soft palate 

 is pulled up, and food has the right of way. In men and apes, the soft 

 palate lies above the epiglottis enabling them to breathe through their 

 mouths with the utmost facility. 



Alysticetes show no great differences from terrestrial mammals in the 

 structure of their pharynx and larynx, except for the fact that the epiglottis 

 is relatively longer. The only real distinction is an opening on the lower 

 side of the thyroid cartilage through which the mucous membrane of the 

 larynx swells out like a large bag at the lower side of the trachea. Although 

 this phenomenon was discovered by Hunter as long ago as 1 787, its exact 

 significance is still not known. It is, however, thought to be some sort of 

 pressure-regulating structure. 



The larynx of an Odontocete, however, differs greatly in structure from 

 that of terrestrial mammals, so much so, in fact, that even the first whale 

 anatomist was struck by it. For this is what Bartholinus had to say about 

 the larynx of the porpoise in his Historarium anatomicarum rariorum (1654) : 

 Larynx singularis figurae, anserinum caput refert — the strange larynx resembles 

 the head of a goose. In fact, in all Odontocetes two of the laryngeal 

 cartilages are greatly elongated and beak-shaped: the epiglottis, and the 

 arytenoid cartilage above it. Often the elongated epiglottis looks like an 

 open gutter covered by the arytenoid cartilage, the two together forming a 

 fairly narrow pipe which, however, can be distended by muscles (Fig. 85). 

 In practically all Odontocetes, there is a swelling at the tip of the epiglottis 

 which looks something like a collar stud. The only exception is the Pilot 

 Whale whose epiglottis is shorter and in which it is the arytenoid cartilage 

 which holds the 'stud'. However, the function of the two structures is 

 identical. 



If we now look at the throat itself, we find that the elongated 'beak' of 

 the epiglottis protrudes into the inferior part of the sloping nasal duct, 

 the soft palate being extended towards the rear and being considerably 

 thickened at its posterior edge. The thickening is continued along the 

 lateral walls of the pharynx, and also just over the entrance to the 

 oesophagus. Hence the nasal passage is greatly narrowed down at its 



