Lull— Fan ctions of the '^Sacral Braln^^ in Dinosaurs. 47Y 



of the elephant, hippopotamus, and rhinoceros does not 

 bear this out, and even in the Pleistocene the largest 

 elephants, such as Elephas imperator, were southern 

 forms compared with the smaller, cold-adapted E. primi- 

 genius. With marine creatures Branca 's statement 

 seems more nearly true, for the walrus and huge sea- 

 elephants are both adapted to cold waters, and the same 

 is true of the right whales, Balcena mysticetus and B. 

 australis. The sperm whale, on the other hand, is trop- 

 ical or subtropical, not occurring, except accidentally, 

 in the polar regions (Flower and Lydekker), while the 

 great rorquals (Balaenoptera) are found in all seas 

 except the Arctic and probably the Antarctic also. Of 

 the deer, perhaps the largest living form is the Alaskan 

 moose, while no bears in existence can compare in mag- 

 nitude with the great Kadiak bear of the same region. 

 But this argument loses weight if the dinosaurs were 

 not warm-blooded, and though the supposition that they 

 were has been advanced, it is not susceptible of proof. 

 It is within the range of possibility that the temperature 

 of the more agile dinosaurs rose appreciably during the 

 time of their activity, as in many of the so-called cold- 

 blooded (poikilothermous) creatures today, but whether 

 or no any dinosaurs had a mechanism for even a partial 

 maintenance of temperature is unknown. If their bodily 

 heat varied with that of the surrounding air, the greater 

 bulk and hence relatively smaller radiating surface would 

 render them less susceptible to rapid temperature 

 changes, and thus prolong their time of activity by tiding 

 over a brief drop in temperature, but would hardly be 

 available in an extended cooler period. That increase of 

 size in dinosaurs was an adaptation for the conservation 

 of energy, and in this way reduced the relative amount 

 of nourishment necessary for their maintenance, seems 

 hardly probable. 



