48 A BOOK OF WHALES 



Dr. Mtiller, however,^ would answer the question, 

 which we asked some few lines above, in another 

 fashion. He is of opinion that the whalebone whales 

 breathe more with the thoracic musculature and less 

 with the diaphragm than do the toothed whales. The 

 diaphragm in them is not so purely muscular an 

 organ as it is in those toothed whales in which it has 

 been examined. Hence the greater part of the exer- 

 tions requisite for inspiration are thrown upon the 

 muscles of the trunk. The freedom of the ribs and 

 a consequent shortening of the sternum is favourable 

 to this supposed increased activity. It is also in- 

 geniously suggested by the same authority that the 

 whalebone whales, pursuing as they do minute prey 

 instead of the comparatively large cuttlefish eaten 

 by the bulk of the toothed whales, have to remain 

 longer under water before they can obtain a sufficient 

 supply of their food. The freedom of the ribs, etc., 

 not only allows of a greater extensibility of the 

 alimentary canal, but a greater expansion of the 

 lungs, and, in consequence, a greater indraught of 

 air. Whatever may be the explanation, however, 

 the facts are as stated, 



THE SKULL 



The most obvious and the most remarkable feature 

 of the whale's skull is its asymmetry in the toothed 

 whales. So unintelligible does this aberration from 

 what is normal in mammals appear to be, that it has 



* Quoted on p. 54, where the connection between the respiratory 

 organs and the dwindling sternum is further elaborated. 



