58 A BOOK OF IV ff ALES 



utilised by the tissues through which the retia pass 

 than in the case of a single tube. In fact, in the 

 whale we have a state of affairs which in some degree 

 suggests the respiratory conditions occurring in an 

 insect, where the ramifying tracheae bring the air to 

 the organs individually, instead of as in the bulk 

 of air-breathing animals the air having to be ex- 

 tracted from the blood by the tissues. These large 

 reservoirs of oxygen within the body, and in close 

 relation to various organs which need abundant 

 oxygen, then do away with the need for an in- 

 creased lung surface in these diving animals. But 

 not altogether ; it looks as if the simpler condition 

 of the lung had been retained, for in reptiles the 

 lungs have the same simple unlobulated structure, 

 the increase being simply brought about by an 

 increased length rendered possible by the greater 

 obliquity of the diaphragm. 



THE WHALE'S STOMACH 



It is a highly characteristic feature of whales, and 

 one \vhich is absolutely universal, that they have 

 an exceedingly complicated stomach. In man the 

 stomach is simply a bent, somewhat U-shaped, wide 

 region of the gut ; there is, however, a difference 

 observable in the structure of the lining membrane 

 between what is called the cardiac portion of the 

 organ (so called because it lies nearest to the heart) 

 and the distal pyloric region, out of which opens the 

 intestine. As a rare abnormality, however, the 



