xii Journal of Comparative Neurology. 



"17. The sulcus frontalis mesialis is absent or poorly developed 

 in the brain of the negro." * * * 



"20. The sulcus prsecentralis inferior and the inferior frontal sul- 

 cus are the furrows which are most firmly impressed upon the brain 

 of the apes. In Cebus they alone are present ; in Calithrix there are 

 also traces of the sulcus prEecentralis superior and sulcus fronto- 

 orbitalis; in the baboon there are, in addition, a rudimentary 

 sulcus frontalis superior, and perhaps (?) traces of a sulcus frontalis 

 medius. 



21. In the chimpanzee and the gorilla the sulcus frontalis me- 

 dius is often present in a form precisely similar to that seen in the hu- 

 man brain; in the orang the condition of this sulcus is doubtful; in 

 the gibbon the sulcus frontalis medius is absent. 



22. In the chimpanzee, therefore, the same convolution tiers 

 may be seen as in man with this exception : the superior frontalis is 

 never split into two by a sulcus frontalis mesialis. 



23. The inferior frontal convolution of apes is very different 

 from that in man. 



24. The frontal and orbital sylvian opercula are completely ab- 

 sent in the apes. 



25. Consequently, a portion of the island of Reil is uncovered 

 and exposed on the surface of the cerebrum. 



26. The sulcus fronto-orbitalis of apes corresponds to the ante- 

 rior limiting sulcus of the island of Reil in man. 



27. There are no anterior limbs of the Sylvian fissure in the 

 anthropoid apes. The so-called anterior limb of the Sylvian fissure 

 corresponds to the anterior free border of the fronto-parietal oper- 

 culum. 



28. About the seventh month of foetal life the inferior prsecentral 

 sulcus of the human brain attains a position which it retains unaltered 

 throughout all the subsequent changes of growth ; previous to this it is 

 placed relatively further back on the surface of the hemisphere. 



29. At first it is placed in front of the coronal suture. The 

 sutural line, however, moves forward so that the sulcus ultimately 

 comes to lie behind it. 



30. In the ape cerebrum the inferior praecentral sulcus lies rela- 

 tively much further forwards than in the cerebrum of man. It may 

 be placed subjacent to, or in front of, the coronal line." 



