SENSES AND THE CENTRAL NERVOUS SYSTEM 24I 



cord has a very distinct cervical intumescence; the himbar sweUing is much 

 less prominent. 



While the first descriptions of the Cetacean brain were written by Ray 

 in 1 67 1 and Tyson in 1680, both of whom dissected a porpoise, the earliest 

 comparative account to have remained of any real value is Tiedemann's 

 (1826). True his description contained some errors, but these were put 

 right twenty years later by Stannius, who also made a study of the brains 

 of porpoises. Mysticete brains are, of course, more difficult to come by, 

 and though Hunter gave a first, superficial, description in 1787, it took 

 many years before a specimen made its first appearance in a laboratory. 

 In 1879, Prof. Aurivilius of the University of Uppsala was sent the brain 

 of a Rorqual by a Norwegian whaling station, but as he considered it too 

 valuable for dissection, he kept it in the museum, where it probably still 

 is to this day. Fortunately, the Norwegian station continued to supply 

 whale brains, and in 1885 Guldberg was able to give a full account, in 

 the course of which he mentioned the great difficulties involved in dissect- 

 ing so delicate and fragile an organ surrounded by such hard bone. It took 

 him five hours of intensive work to remove the brain from the skull, and 

 even though modern instruments have reduced the time, the removal of a 

 whale's brain is still one of the toughest tasks a zoologist has to tackle. 

 Even so, we now have fairly full descriptions of the brains of a number of 

 Cetaceans. 



Everyone looking at the brain of a whale or dolphin for the first time 

 is struck by the fact that the brain is so compressed from front to back 

 (Figs. 125, 126). In Mysticetes, it is as wide as it is long, but in Odonto- 

 cetes its width actually exceeds its length and, in addition, it is very 

 peculiarly cvu'ved. All these characteristics do not, however, affect the 

 internal structure and function of the brain, but simply arise from the 

 peculiar telescoping of the Cetacean skull bones which we have discussed 

 in Chapter 2. What does affect the function of the brain is the equally 

 striking fact that the cerebrum is so large and extends so far back that, for 

 instance, in Common Dolphins it completely covers the cerebellum, and 

 in other Odontocetes it covers most of it. (In Mysticetes, on the other hand, 

 the top of the cerebellum is clearly visible.) A third striking characteristic 

 of the Cetacean brain is its exceptionally convoluted appearance. This was 

 first noticed in 1671 by Ray, who thought it pointed to a high state of 

 mental development. The Dutch neurologist, Prof Jelgersma, was so 

 struck by the resemblance between porpoise and human brains, that he 

 devoted his old age to the comparative study of the brains of porpoises, 

 sea-cows and common otters. In 1934, at the age of seventy-four, he 

 published the results in a book entitled Das Gehirn der Wassersaugetiere (The 

 brain of aquatic mammals). 



