viii Journal of Comparative Neurology. 



They are not developed as primitive deficiencies in the orbital oper- 

 culum. 



11. The posterior insula is not connected with the extremity of 

 the temporal lobe, as Eberstaller has asserted, but with the limbic 

 lobe. 



12. On the surface of the foetal insula there appear three radial 

 furrows which correspond in every respect with the three " Primar- 

 furchen " on the outer surface of the mantle (viz: the fissure of Ro- 

 lando, the inferior praecentral sulcus, and the vertical limb of the 

 intra-parietal sulcus). The radial furrows on the insula clearly belong 

 to the same fissural system and intermediate links between the three 

 radial fissures on the outer surface of the hemisphere, and the three 

 radial fissures on the insula may exist in the form of secondary sulci, 

 cutting the margin of the fronto-parietal operculum. 



13. The fissure of Rolando is clearly the proper boundary of 

 the frontal lobe. Above, it is only separated from the calloso-mar- 

 ginal fissure, which bounds the lobe internally, by a narrow, but su 

 perficial gyrus; below, the inferior transverse furrow of Eberstaller 

 acts as an intermediate link between it and the sulcus centralis insulae. 

 The sulcus centralis insulae and the calloso marginal sulcus are brought 

 into close relationship at the anterior perforated spot on the base of 

 the brain. An almost continuous fissural system, therefore, marks 

 out the limits of the frontal portion of the cerebrum. 



14. The temporal pole is formed entirely by the forward growth 

 of the fore part of the temporal operculum. 



15. In the adult brain the insula is proportionately longer in the 

 male than the female. At all periods of growth it would seem that 

 the insula is relatively longer on the left side than on the right side. 

 In the negro brain it would appear that the insula is relatively shorter 

 than in the European brain. 



16. In the anthropoid ape the so-called anterior limb of the 

 Sylvian fissure is not homologous with either of the anterior limbs in 

 man. 



I 7. In the chimpanzee and orang there are only two opercula, 

 viz: the fronto-parietal and the temporal. The frontal and orbital 

 opercula of the human brain are entirely absent in the anthropoid 

 cerebrum. 



18. Restricting the term insula to that part of the hemisphere 

 surface which is concealed from view by opercula, the extent of this 

 area in the ape is very much less than in man. The central index is 

 18.2 in the chimpanzee and 21.5 in the orang ; in man the central 



