454 'Journal of Comparative Neurology and Psychology. 



to associative and intelligent actions. That, in fact, is the case 

 with those mammals in which the neencephalon includes much 

 more than half the bulk of the entire brain. But in many families 

 there is very little advance beyond the condition prevailing in 

 birds, for example in the hedgehogs and the moles. In the mice, 

 the rabbits, in fact in nearly all the rodents the two parts are 

 about evenly balanced. What we know of the intelhgence of 

 these animals — and that is little enough — is in very close accord 

 with the condition of the brain. In fig, 4 is represented a 

 hedgehog brain in which one may readily see that the two portions 

 of the brain, somewhat separated from one another by a horizontal 

 furrow, are of approximately equal size. 



It would exceed the limits within which I must keep, if I should 

 more than cursorily outline the task of him who undertakes, 

 through anatomy, to be of use to mammahan psychology. The 



Fig. 4. Brain of a hedgehog. 



oldest part of the neencephalon, namely the olfactory and parolfac- 

 tory or oral centers which are present in reptiles, persists as the 

 hornof Ammon. As shown in fig. 5, with the evolution of the other 

 portions of the cortex it becomes pushed to the median plane and 

 rolled upon itself. It is very probable that the function of this part 

 of the brain, which because of its age has been designated as 

 the archipallium in distinction to the remaining cortex or neopal- 

 lium, remains unchanged, but unfortunately we lack any far-reach- 

 ing observations on animals which have been subjected to opera- 

 tions. After all, we know that the archipallium is well developed 

 only in those animals which are guided to a large extent by their 

 olfactory sense and that it is smaller but not lacking in animals 

 which have an atrophied olfactory mechanism. The whales have 

 rudimentary olfactory nerves but the archipallium has not entirely 

 disappeared. Since we know that also the central connections 

 of the oral mechanism (around the snout) terminate here, the 



