142 WHALES 



Structure of the lungs of twelve different species of Cetaceans and, to some 

 extent at least, of how that structure is adapted to an aquatic form of 

 existence. 



One of the first characteristics, little connected with breathing or 

 diving, which struck the investigators, was purely negative, though of 

 positive value to the animals : the complete absence of mucous (goblet) 

 cells in the epithelium of the trachea and the bronchi, and their almost 

 complete absence in the glands terminating in the air passages. Moreover, 

 the bronchioles and other parts of the lung are somewhat deficient in 

 lymphoid tissue, and the trachea is said to be lacking in cilia. Since cilia 

 have, however, been found in the bronchi, their alleged absence in the 

 trachea may hav^e been due to the fact that the histological material 

 examined was poor. Bearing in mind that all the above characteristics 

 are associated with the removal of dust and bacteria from the air passages, 

 and that dust cells have never been discovered in whales or dolphins, it 

 becomes clear that in the clean and moist environment in which these 

 animals live, they can dispense with structures that are essential to 

 animals living in adry, dusty and germ-ridden atmosphere. Not surprisingly, 

 \V. Ross Cockrill, a veterinary surgeon who inspected many thousands 

 of whales in the Antarctic, never once diagnosed an infection of their air 

 passages. (In 1959, pneumonia was first diagnosed in a Fin Whale.) And 

 we, who use up considerable quantities of handkerchiefs, who are plagued 

 by colds and bronchitis, have every reason to be jealous of animals which, 

 according to the Russian biologist Tomilin (1955), are quite unable even 

 to cough. He found that in dolphins the so-called coughing reflex is 

 completely absent, and that water which accidentally finds its way into the 

 air passages is removed during ordinary exhalation. We have, however, 

 seen that the blow of a whale is so intense that it may almost be called a 

 cough. 



Another characteristic, on the other hand, is directly associated with 

 diving: the structure of the bronchi. We have already seen that in terres- 

 trial mammals these ramifications of the trachea have cartilage supports 

 at the beginning, but not at their terminal branches. Now in Cetaceans 

 the cartilage, in the form of spirals, rings or irregular pieces, reaches right 

 down to the alveolar sacs. There is only one known exception to this rule, 

 viz. a species oï Berardius, found off' Japan, a relative of the Bottlenose 

 Whale, in which the cartilage support stops higher up. 



As a result of this extra support, all the air pipes are provided with a 

 rigid wall which is constantly kept open and hence is far less sensitive to 

 pressure changes than the rest rjf the lungs. This, as we shall see, is a great 

 advantage, particularly during the strong fluctuations in pressure which 

 occur in the course of vertical dives. 



