SENSES AND THE CENTRAL NERVOUS SYSTEM 249 



Figure 128. Top view of the brain of a Bottlenose Whale. {Kiikenthal, i88g. 



cells and thus the site of cerebration, constitutes a rather thin cover of the 

 cerebral hemispheres. It is, in fact, a surface, with the result that its 

 area decreases (relatively in size) the greater the total mass of the brain 

 becomes. To compensate for this deficiency, the cortex of big animals is 

 thrown up into a correspondingly larger number of folds, thus increasing 

 the total surface area. The fact that the cortex of porpoises shows almost 

 as many folds as the human cortex may possibly be due to its exceptional 

 thinness (Jelgersma, 1934), but we must remember that the number of 

 convolutions is related to the absolute size of the brain, so that it 

 depends not only on the size of the animal, but also on its stage of 

 cephalization. 



Must we assume that porpoises. Sperm Whales and dolphins, by virtue 

 of their highly convoluted brains, have mental capacities akin to those of 

 man, and that Adriatic fishermen who claim that dolphins are good 

 Christians are not so far off' the mark ? While we cannot go all the way 

 with them, we can nevertheless assert that the high development of their 

 brain clearly indicates that these animals have a strongly centralized 

 nervous system, and that many Cetacean reactions are more dependent 

 on the brain than those of other mammals. Some scholars have pointed to 

 the very important role that the acoustic sense plays in their lives, and see 

 in its high degree of development a large contributory factor to the growth 

 of the brain and of the cortex, in particular. On the other hand, sight is 



