338 DE- G- ELLIOT SMITH ON 



that tlie general growth of tlie pallium may liave some influence in the production of 

 the crucial sulcus. 



Apart from this apparent difference in the extent of the excitable areas of the cortex, 

 there are other differences between the pallia in the contrasted brains. 



If we compare the size of the brain in Ilyrmecophaga and Caiiis, we shall find a 

 striking contrast between the two organs. In his valuable monograph upon the weight 

 of the brain in mammals, Max Weber* gives the weight of the brain in grammes as 

 comjiared to the body-weight in four specimens of the Great Ant-eater as follows :— 



Percentage of 



Brain- Body- Braiii-woiglit 



weight, ■weight. to Botly-weight. 



Myrmecophmja juhuta, % 75 : 20,800 0-36% 



$ 84-5:25,500 0-33% 



? 87 : 23,000 0-37 7o 



? 84 : 28,086 0-29% 



}) 



From the same lists 1 select for comparison the brain-weights of four Dogs whose 

 body-weights approximate to those of the Ant-eaters, and exj)ress them in a similar 

 manner thus : — 



Percentage of 

 Brain- Body- JJrain-weighfc 



weight, weight. to Body-weight. 



Canisfam.: Bernhard, 'i ] 16 : 28,000 0-41% 



Canis fum. -. Sat/ax venaticiis -f- Extrarius 



aquaticus ieme novtE, S I'^'T' : 27,500 0-39% 



Canis faw.: ditto, S 9« = 25,000 0-39% 



Can is fum. : Molonossus 95 : 2 1 ,000 0-45 % 



In all of these Dogs there is a most decided superiority in the brain-weight over that 

 of the Ant-eaters. 



The brain-weight in Dogs is exceedingly variable, as Weber's tables amply demonstrate, 

 but in all Dogs approaching the size of a Mijrmecophaga there is a very decided superiority 

 in the weight of the Dog's brain over that of the Edentata. Among otlier sj)ecies and 

 genera this superiority is even more striking. Thus in Cams juhatus, according to Weber, 

 we find a brain Aveighing IGO grms. in an animal of only 23,G00 grms., i. e. a brain 

 0'7 7o of the body-weight, and in Felis panlas a brain of 130 grms. in an animal of 

 23,820 grms., or O'Si 7o of the body-weight. On the other hand, in a Hycena striata 

 weighing 28,750 grms., or more than the heaviest of the four Ant-eaters, Weber found a 

 brain weighing nearly 81 grms., or 0-28 7^ of the body-weight. This, however, must 

 have been a very exceptional case, for in another specimen of the same species and of 

 the same sex he found a brain of 89 grms. (i. e. heavier than the brain of any of the 

 Ant-eaters), while the animal weighed merely 17,500 grms., thus giving a brain-weight 

 which is 0-508 7^ of the body-weight. 



* Max Weher, " Yorstudien iiber das Hirngewicht der iSaugethicre," Separat-Abdruck aus Festschrift fiir Carl 

 Gegenbaur, Leipzig, 1S96. 



