Chapter Twelve 



Other Soft Tarts and Physiological Features 



1 HE WRITER has not concerned himself, save very incidentally, with 

 any part of the physiology of aquatic mammals other than of the mus- 

 cular system, nor with the internal organs. Nevertheless, the present 

 contribution would be very incomplete without including some consid- 

 eration of these features, because some of the most interesting problems 

 concerning the Cetacea are involved with them. Accordingly it is aimed 

 to offer brief mention of what seem to be the most important of these 

 questions, and to point out some of the possibilities, without any at- 

 tempt at an exhaustive consideration. These points have frequently been 

 discussed with Doctors E. K. Marshall and G. B. Wislocki of the Johns 

 Hopkins Medical School, who are working on some of them, and to 

 whom I am accordingly obligated. 



There is a veritable host of interesting problems concerned with the 

 physiology of the more highly modified aquatic mammals, especially 

 the Cetacea, which are particularly difficult to solve largely for the rea- 

 son that it is not easy to experiment on the live animal, and because 

 they involve alterations in quality from those encountered in ourselves, 

 so that a very real obstacle is our inability to compare conditions with 

 what we know obtains in the case of terrestrial mammals. Perhaps the 

 most important, or at least spectacular, of these questions is concerned 

 with the ability of some whales to descend to depths in excess of a mile, 

 and to remain thereabouts for more than an hour. How do they with- 

 stand the pressure ? How do they take down sufficient oxygen ? More 

 important still, how do they get rid of the carbon dioxide in the blood ? 

 If we hold our breath for a minute we are in distress, not because we 

 need more oxygen at once, but because there is imperative need to dis- 

 pose of the accumulation of carbon dioxide. 



Another point, of particular interest to students of the human brain, 

 is that although the porpoise apparently has less need for intelligence 

 than almost any other living mammal, and little if any more than had 

 the ichthyosaurs, the convolutions of its brain are more marked than in 

 man, thus indicating the probability that this character is not as signifi- 

 cant of intelligence as many now believe. Other details of the cetacean 



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